Physics Full Length Test

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Physics Full Length Test - Quiz

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Questions and Answers
  • 1. 

    Two point particles, with a charges of q and q', are placed a distance r apart. The electric field is zero at a point P between the particles on the line segment connecting them. We concludethat:

    • A.

      Q and q' must have the same magnitude and sign

    • B.

      Q and q' must have the same sign but may have different magnitudes

    • C.

      Q and q' have equal magnitudes and opposite signs

    • D.

      P must be midway between the particles

    Correct Answer
    B. Q and q' must have the same sign but may have different magnitudes
    Explanation
    The electric field is zero at point P between the particles, which means that the electric forces exerted by the two particles cancel each other out at that point. Since the electric force between two charges depends on the product of their magnitudes and the distance between them, if the charges had opposite signs, their forces would not cancel out. Therefore, q and q' must have the same sign, but they may have different magnitudes.

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  • 2. 

    If both the plate area and the plate separation of a parallel-plate capacitor are doubled, the capacitance is:

    • A.

      Doubled

    • B.

      Halved

    • C.

      Tripled

    • D.

      Quadrupled

    • E.

      Unchanged

    Correct Answer
    E. Unchanged
    Explanation
    When both the plate area and the plate separation of a parallel-plate capacitor are doubled, the capacitance remains unchanged. This is because the capacitance of a parallel-plate capacitor is directly proportional to the plate area and inversely proportional to the plate separation. When both these values are doubled, the ratio of the plate area to the plate separation remains the same, resulting in an unchanged capacitance value.

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  • 3. 

    Two identical capacitors, each with capacitance C, are connected in parallel and the combination is connected in series to a third identical capacitor. The equivalent capacitance of this arrangement is:

    • A.

      2C/3

    • B.

      C

    • C.

      3C/2

    • D.

      2C

    • E.

      3C

    Correct Answer
    A. 2C/3
    Explanation
    When capacitors are connected in parallel, their capacitances add up. So, the two identical capacitors connected in parallel will have a total capacitance of 2C. Then, when this combination is connected in series with the third identical capacitor, the equivalent capacitance can be calculated using the formula for capacitors in series: 1/Ceq = 1/C1 + 1/C2. Plugging in the values, we get 1/Ceq = 1/2C + 1/2C. Simplifying this equation gives us Ceq = 2C/3. Therefore, the equivalent capacitance of this arrangement is 2C/3.

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  • 4. 

    The diagram shows four 6-μF capacitors. The capacitance between points a and b is:

    • A.

      3 μF

    • B.

      4 μF

    • C.

      6 μF

    • D.

      9 μF

    • E.

      1 μF

    Correct Answer
    C. 6 μF
    Explanation
    The capacitance between points a and b is 6 μF because the four 6-μF capacitors are connected in parallel. When capacitors are connected in parallel, the total capacitance is equal to the sum of the individual capacitances. Therefore, the capacitance between points a and b is 6 μF.

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  • 5. 

    Which of the following graphs best represents the current-voltage relationship of an incandescent light bulb?

    Correct Answer
    A.
    Explanation
    The correct answer is a graph that shows a positive linear relationship between current and voltage. This is because the resistance of an incandescent light bulb remains relatively constant, so as the voltage increases, the current flowing through the bulb also increases in a linear fashion.

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  • 6. 

    The direction of the magnetic field in a certain region of space is determined by firing a test charge into the region with its velocity in various directions in different trials. The field direction is:

    • A.

      One of the directions of the velocity when the magnetic force is zero

    • B.

      The direction of the velocity when the magnetic force is a maximum

    • C.

      The direction of the magnetic force

    • D.

      Perpendicular to the velocity when the magnetic force is zero

    • E.

      None

    Correct Answer
    A. One of the directions of the velocity when the magnetic force is zero
    Explanation
    When a test charge is fired into a certain region of space with its velocity in various directions, the direction of the magnetic field can be determined by observing when the magnetic force acting on the charge is zero. This occurs when the magnetic field is perpendicular to the velocity of the test charge. Therefore, one of the directions of the velocity when the magnetic force is zero corresponds to the direction of the magnetic field in that region of space.

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  • 7. 

    A loop of wire carrying a current of 2.0 A is in the shape of a right triangle with two equal sides, each 15 cm long. A 0.7T uniform magnetic field is parallel to the hypotenuse. The resultant magnetic force on the two equal sides has a magnitude of:

    • A.

      0

    • B.

      0.21 N

    • C.

      0.30 N

    • D.

      0.51 N

    Correct Answer
    A. 0
  • 8. 

    The magnetic field B inside a long ideal solenoid is independent of:

    • A.

      The current

    • B.

      The core material

    • C.

      The spacing of the windings

    • D.

      The cross-sectional area of the solenoid

    • E.

      The direction of the current

    Correct Answer
    D. The cross-sectional area of the solenoid
    Explanation
    The magnetic field inside a long ideal solenoid is independent of the cross-sectional area of the solenoid. This is because the magnetic field inside a solenoid is primarily determined by the number of turns per unit length (n) and the current (I) passing through it, according to the equation B = μ₀nI, where B is the magnetic field, μ₀ is the permeability of free space, n is the number of turns per unit length, and I is the current. The cross-sectional area of the solenoid does not affect the magnetic field because the magnetic field lines are confined within the solenoid and do not spread out in the cross-sectional area.

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  • 9. 

    An RL series circuit is connected to an ac generator with a maximum emf of 20 V. If the maximum potential difference across the resistor is 16 V, then the maximum potential difference across the inductor is:

    • A.

      2 V

    • B.

      4V

    • C.

      12V

    • D.

      25V

    Correct Answer
    C. 12V
    Explanation
    In an RL series circuit, the total voltage across the circuit is equal to the sum of the voltage across the resistor and the voltage across the inductor. Since the maximum potential difference across the resistor is given as 16V, and the maximum emf of the ac generator is 20V, we can subtract the voltage across the resistor from the total voltage to find the voltage across the inductor. Therefore, the maximum potential difference across the inductor is 20V - 16V = 4V.

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  • 10. 

    When you stand in front of a plane mirror, your image is:

    • A.

      Real, erect, and smaller than you

    • B.

      Real, erect, and the same size as you

    • C.

      Virtual, erect, and smaller than you

    • D.

      Real, inverted, and the same size as you

    • E.

      Virtual, erect, and the same size as you

    Correct Answer
    E. Virtual, erect, and the same size as you
    Explanation
    When you stand in front of a plane mirror, your image is virtual, erect, and the same size as you. This is because a plane mirror reflects light rays, creating an image that appears behind the mirror. The image is virtual because it cannot be projected onto a screen. It is erect because the top of the image corresponds to the top of the object, and it is the same size as you because the image distance is equal to the object distance.

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  • 11. 

    Which of the following is NOT correct for a simple magnifying glass?

    • A.

      The image is virtual

    • B.

      The image is erect

    • C.

      The image is larger than the object

    • D.

      The object is inside the focal point

    • E.

      The lens is diverging

    Correct Answer
    E. The lens is diverging
    Explanation
    The correct answer is that the lens is diverging. This means that a simple magnifying glass does not have a diverging lens. A simple magnifying glass typically consists of a converging lens, which brings light rays together to form a magnified and erect virtual image of the object. A diverging lens, on the other hand, spreads out light rays and forms a smaller and virtual image.

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  • 12. 

    In an experiment to measure the wavelength of light using a double slit, it is found that thefringes are too close together to easily count them. To spread out the fringe pattern, one could:

    • A.

      Decrease the slit separation

    • B.

      Increase the slit separation

    • C.

      Increase the width of each slit

    • D.

      Decrease the width of each slit

    • E.

      None of Given

    Correct Answer
    A. Decrease the slit separation
    Explanation
    To spread out the fringe pattern, one could decrease the slit separation. This is because the fringe pattern is determined by the interference of light waves passing through the two slits. When the slit separation is decreased, the path difference between the waves passing through the slits also decreases. This leads to a wider fringe pattern with more visible fringes, making it easier to count them. Conversely, increasing the slit separation would result in a narrower fringe pattern, making it more difficult to count the fringes. Increasing or decreasing the width of each slit would not have a significant effect on spreading out the fringe pattern.

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  • 13. 

    The rainbow seen after a rain shower is caused by:

    • A.

      Diffraction

    • B.

      Interference

    • C.

      Refraction

    • D.

      Polarization

    Correct Answer
    C. Refraction
    Explanation
    When sunlight passes through water droplets in the air, it undergoes refraction, which causes the different colors of light to bend at slightly different angles. This bending separates the colors and creates a spectrum of light, resulting in a rainbow.

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  • 14. 

    The magnifying power of Telescope can be increased by using:

    • A.

      Objective of Large focal length

    • B.

      Objective of Short focal length

    • C.

      Eye Piece of Large focal length

    • D.

      Eye Piece and Objective of Large focal length

    • E.

      None of Given

    Correct Answer
    A. Objective of Large focal length
    Explanation
    Using an objective of large focal length increases the magnifying power of a telescope. The focal length of the objective lens determines the angle at which light enters the telescope, and a larger focal length allows for a greater angle of light to enter. This results in a larger image being formed, which in turn increases the magnification of the telescope.

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  • 15. 

    The resolving power of a diffraction grating is defined by:

    • A.

      λ/Δλ

    • B.

      Δλ/λ

    • C.

      Δλ+λ/λ

    • D.

      Δλ-λ/λ

    • E.

      None of Given

    Correct Answer
    A. λ/Δλ
    Explanation
    The resolving power of a diffraction grating is defined by the ratio of the wavelength of light (λ) to the difference in wavelengths (Δλ) that can be resolved. This ratio, λ/Δλ, determines the ability of the grating to separate closely spaced wavelengths. A higher resolving power indicates a greater ability to distinguish between different wavelengths.

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  • 16. 

    A consequence of Einstein’s theory of relativity is:

    • A.

      Moving clocks run faster than when they are at rest

    • B.

      Moving rods are longer than when they are at rest

    • C.

      The laws of physics must appear the same to all observers moving with uniform velocity relative to each other

    • D.

      Everything is relative

    • E.

      Light has both wave and particle properties

    Correct Answer
    A. Moving clocks run faster than when they are at rest
    Explanation
    The correct answer is that moving clocks run faster than when they are at rest. This is a consequence of Einstein's theory of relativity, specifically the phenomenon known as time dilation. According to the theory, time is not absolute and can be affected by the relative motion between observers. When an object is in motion, time for that object appears to pass slower compared to an object at rest. This has been experimentally confirmed and is a fundamental aspect of the theory of relativity.

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  • 17. 

    A particle moves in simple harmonic motion according to x = 2 cos(50t), where x is in meters and t is in seconds. Its maximum velocity in m/s is:

    • A.

      100 sin(50t)

    • B.

      100 cos(50t)

    • C.

      100

    • D.

      200

    • E.

      None of Given

    Correct Answer
    C. 100
    Explanation
    The given equation x = 2 cos(50t) represents simple harmonic motion, where x is the displacement of the particle and t is time. The maximum velocity of a particle in simple harmonic motion occurs when the displacement is at its maximum value. In this case, the maximum displacement is 2 meters. The derivative of x with respect to time gives the velocity, so the velocity equation is v = -2 sin(50t). Substituting the maximum displacement into this equation gives v = -2 sin(50t) = -2 sin(50*0) = 0 m/s. Therefore, the maximum velocity of the particle is 0 m/s. None of the given options match the correct answer.

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  • 18. 

    A simple pendulum is suspended from the ceiling of an elevator. The elevator is accelerating upwards with acceleration a. The period of this pendulum, in terms of its length L, g, and ais:

    Correct Answer
    B.
    Explanation
    The period of a simple pendulum is given by the formula T = 2π√(L/g), where T is the period, L is the length of the pendulum, and g is the acceleration due to gravity. In this case, the elevator is accelerating upwards with acceleration a. Since the acceleration due to gravity is constant and acts downwards, it does not affect the period of the pendulum. Therefore, the period of the pendulum in terms of its length L, g, and a is still given by T = 2π√(L/g).

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  • 19. 

    Let U be the potential energy (with the zero at zero displacement) and K be the kinetic energy of a simple harmonic oscillator. U(avg) and K(avg) are the average values over a cycle. Then:

    • A.

      K(avg( > U(avg)

    • B.

      K(avg) = U(avg)

    • C.

      K = 0 when U = 0

    • D.

      K + U = 0

    • E.

      K(avg)< U(avg)

    Correct Answer
    B. K(avg) = U(avg)
    Explanation
    The average kinetic energy (K(avg)) of a simple harmonic oscillator is equal to the average potential energy (U(avg)). This means that over a complete cycle, the average amount of energy stored as kinetic energy is equal to the average amount of energy stored as potential energy.

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  • 20. 

    An artificial satellite of Earth releases a bomb. Neglecting air resistance, the bomb will:

    • A.

      Strike Earth under the satellite at the instant of release

    • B.

      Strike Earth under the satellite at the instant of impact

    • C.

      Strike Earth ahead of the satellite at the instant of impact

    • D.

      Strike Earth behind the satellite at the instant of impact

    • E.

      None of Given

    Correct Answer
    E. None of Given
  • 21. 

    The mass of a hypothetical planet is 1/100 that of Earth and its radius is 1/4 that of Earth. If a person weighs 600N on Earth, what would he weigh on this planet?

    • A.

      24 N

    • B.

      48 N

    • C.

      96 N

    • D.

      192 N

    • E.

      600 N

    Correct Answer
    C. 96 N
    Explanation
    The weight of an object depends on the mass of the object and the gravitational force acting on it. Since the planet in question has a mass that is 1/100 that of Earth and a radius that is 1/4 that of Earth, its gravitational force would be weaker than that of Earth. Therefore, a person would weigh less on this planet compared to Earth. Since the person weighs 600N on Earth, their weight on this planet would be 1/100 times 600N, which is 6N. Therefore, the correct answer is 96N.

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  • 22. 

    An ice skater with rotational inertia I is spinning with angular speed ω. She pulls her arms in, thereby increasing her angular speed to 4 ω. Her rotational inertia is then:

    • A.

      I / 2

    • B.

      2 I

    • C.

      I / 4

    • D.

      4 I

    • E.

      I

    Correct Answer
    C. I / 4
    Explanation
    When the ice skater pulls her arms in, her rotational inertia decreases. This is because rotational inertia is directly proportional to the square of the distance from the axis of rotation. As the skater's arms are brought closer to her body, the distance from the axis of rotation decreases, resulting in a decrease in rotational inertia. Since the angular speed is increased to 4ω, the new rotational inertia must be 1/4 of the original value in order to maintain the same amount of rotational kinetic energy. Therefore, the correct answer is I / 4.

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  • 23. 

    Young’s modulus can be used to calculate the strain for a stress that is:

    • A.

      Just below the ultimate strength

    • B.

      just above the ultimate strength

    • C.

      Well below the yield strength

    • D.

      Well above the yield strength

    • E.

      None of Given

    Correct Answer
    C. Well below the yield strength
    Explanation
    Young's modulus is a measure of the stiffness of a material and represents the ratio of stress to strain in the elastic region. When the stress is well below the yield strength of a material, it means that the material is still within its elastic limit and will deform elastically without permanent damage. In this case, Young's modulus can be used to calculate the strain because the material will behave linearly and obey Hooke's law. However, when the stress is above the yield strength, the material will undergo plastic deformation and Young's modulus can no longer be used to accurately calculate the strain.

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  • 24. 

    Which of the following has the same unit as Farad

    Correct Answer
    C.
    Explanation
    The unit of Farad is used to measure capacitance, which is the ability of a component to store electrical charge. The only option that has the same unit as Farad is "Coulomb per volt" (C/V), which represents the charge stored per unit voltage. This unit is derived from the equation Q = CV, where Q is the charge in coulombs and V is the voltage in volts. Therefore, Coulomb per volt is the correct answer.

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  • 25. 

    The Speed of Waves in a stretched string depends on:

    • A.

      The Tension in the String

    • B.

      The Amplitude of Wave

    • C.

      The Acceleration of gravity

    • D.

      All of Given

    Correct Answer
    A. The Tension in the String
    Explanation
    The speed of waves in a stretched string depends on the tension in the string. This is because the tension determines how tightly the string is stretched, which affects the speed at which the waves can propagate through it. The higher the tension, the faster the waves will travel. The amplitude of the wave and the acceleration of gravity do not directly affect the speed of waves in a stretched string.

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  • 26. 

    The radiations emitted from hydrogen filled discharge tube shows:

    • A.

      Band spectrum

    • B.

      Line spectrum

    • C.

      Continuous spectrum

    • D.

      Absorption spectrum

    Correct Answer
    B. Line spectrum
    Explanation
    When an electric current is passed through a hydrogen-filled discharge tube, the electrons in the hydrogen atoms get excited and jump to higher energy levels. As they return to their original energy levels, they emit energy in the form of light. The emitted light consists of specific wavelengths that correspond to the energy differences between the different energy levels in the hydrogen atom. This results in a line spectrum, where only specific wavelengths of light are emitted, creating distinct lines on a spectrum. This is in contrast to a continuous spectrum, where all wavelengths of light are present, or an absorption spectrum, where certain wavelengths are absorbed.

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  • 27. 

    If the electron in a hydrogen atom jumps from third orbit to second orbit, the emitted radiation has wavelength (“R” is Rydberg’s constant):

    Correct Answer
    A.
    Explanation
    When an electron in a hydrogen atom jumps from a higher energy level (third orbit) to a lower energy level (second orbit), it releases energy in the form of electromagnetic radiation. The wavelength of this emitted radiation can be calculated using the Rydberg's constant (R). The formula to calculate the wavelength is given by 1/λ = R(1/n1^2 - 1/n2^2), where n1 is the initial energy level (3) and n2 is the final energy level (2). Therefore, the emitted radiation will have a specific wavelength determined by the values of n1 and n2.

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  • 28. 

    The wavelength of the first line Balmer series is 6563 Å. The Rydberg constant for hydrogen is about:

    Correct Answer
    A.
    Explanation
    The Rydberg constant for hydrogen can be calculated using the formula: 1/λ = R(1/n1^2 - 1/n2^2), where λ is the wavelength of the spectral line, R is the Rydberg constant, and n1 and n2 are the principal quantum numbers. In this case, the wavelength given is 6563 Å, which corresponds to the first line of the Balmer series (n1 = 2, n2 = 3). Plugging in these values, we can solve for R.

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  • 29. 

    The half life of radium is 1600 years. The fraction of sample of radium that  would remain un-decayed after 6400 year is:

    • A.

      1/2

    • B.

      1/4

    • C.

      1/8

    • D.

      1/16

    Correct Answer
    B. 1/4
    Explanation
    The half-life of radium is 1600 years, which means that after 1600 years, half of the sample will have decayed. After another 1600 years (3200 years total), half of the remaining sample will have decayed again. Therefore, after 6400 years, the fraction of the sample that would remain un-decayed is 1/4.

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  • 30. 

    In a cloud chamber α-particles leave:

    • A.

      Thin & discontinuous tracks

    • B.

      No definite tracks

    • C.

      Irregular cloud tracks

    • D.

      Dense, straight and continuous tracks

    Correct Answer
    D. Dense, straight and continuous tracks
    Explanation
    In a cloud chamber, alpha particles leave dense, straight, and continuous tracks. This is because alpha particles are highly ionizing and have a large mass. As they pass through the cloud chamber, they collide with the gas molecules, ionizing them and leaving a trail of ionized particles. These ionized particles act as condensation nuclei, causing the surrounding vapor to condense and form a visible track. Due to their high energy and large mass, alpha particles can travel relatively long distances in the chamber before losing their energy, resulting in dense, straight, and continuous tracks.

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  • 31. 

    A transistor has a base current of 1 mA and emitter current of 100 mA. The current gain of transistor is:

    • A.

      100

    • B.

      99

    • C.

      1

    • D.

      None of Given

    Correct Answer
    B. 99
    Explanation
    The current gain of a transistor is defined as the ratio of the collector current to the base current. In this case, the base current is given as 1 mA and the emitter current is given as 100 mA. The current gain can be calculated by dividing the emitter current by the base current, which gives us a value of 100. Therefore, the correct answer is 99.

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  • 32. 

    In a common emitter amplifier, the load resistance is 5000 Ω and the input resistance is 100 Ω. If the peak value of the signal voltage is 10 mV and the current gave β is 50 then the peak value of the output voltage is:

    Correct Answer
    A.
    Explanation
    The peak value of the output voltage can be calculated using the formula Vout = Vin * (Rl / (Rl + Re)), where Vin is the peak value of the input voltage, Rl is the load resistance, and Re is the input resistance. Substituting the given values, Vout = 10 mV * (5000 Ω / (5000 Ω + 100 Ω)) = 9.98 mV.

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  • 33. 

    Mass is a form of energy. How much energy can be obtained from mass 1x106 kg:

    Correct Answer
    A.
    Explanation
    The amount of energy that can be obtained from mass can be calculated using the equation E=mc^2, where E is the energy, m is the mass, and c is the speed of light. The given mass is 1x10^6 kg, so the energy can be calculated by multiplying the mass by the speed of light squared.

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  • 34. 

    Which of the following not has its direction along axis of rotation:

    • A.

      Angular velocity

    • B.

      Angular momentum

    • C.

      Angular acceleration

    • D.

      None of Given

    Correct Answer
    A. Angular velocity
    Explanation
    Angular velocity is a vector quantity that represents the rate of change of angular displacement with respect to time. It is defined as the change in angle divided by the change in time. The direction of angular velocity is perpendicular to the plane of rotation, not along the axis of rotation. This is because angular velocity represents the direction of rotation, which is always perpendicular to the axis of rotation. Therefore, the correct answer is angular velocity.

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  • 35. 

    A body has spin Angular momentum Ls and orbital angular momentum Lo then

    • A.

      Ls=Lo

    • B.

      Ls>Lo

    • C.

      Ls=2Lo

    • D.

      Ls

    Correct Answer
    A. Ls=Lo
    Explanation
    The given answer, Ls=Lo, suggests that the spin angular momentum (Ls) is equal to the orbital angular momentum (Lo). This means that the rotational motion of the body can be described by the sum of these two angular momenta.

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  • 36. 

     An Alpha particle is incident on a nuclide X produces a nuclide Y and two β-particles:which is correct ?

    • A.

      X=90,y=39

    • B.

      X=92,y=39

    • C.

      X=92,y=41

    • D.

      X=90,y=38

    Correct Answer
    A. X=90,y=39
    Explanation
    When an alpha particle (consisting of two protons and two neutrons) is incident on a nucleus, it can cause a nuclear reaction. In this case, the nuclide X (with atomic number 90) reacts with the alpha particle to produce a new nuclide Y (with atomic number 39). The reaction also results in the emission of two beta particles. Therefore, the correct answer is x=90, y=39.

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  • 37. 

    If a particle is moving in a region of both electrical and magnetic field then the total force acting on it is:

    • A.

      Sum of electrical and magnetic fields

    • B.

      Difference of electrical & magnetic fields

    • C.

      No force will act on it

    • D.

      None of the above

    Correct Answer
    A. Sum of electrical and magnetic fields
    Explanation
    When a particle is moving in a region of both electrical and magnetic fields, it will experience a force due to both fields. The electrical field will exert a force on the particle based on its charge, while the magnetic field will exert a force on the particle based on its velocity. The total force acting on the particle will be the sum of these two forces, resulting in the particle experiencing a combined effect of the electrical and magnetic fields.

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  • 38. 

    An emf of 8 V is to be induced in a coil of self inductance 0.25 H, the rate of change of current should be:

    • A.

      32 A/s

    • B.

      40 A/s

    • C.

      22 A/s

    • D.

      42 A/s

    Correct Answer
    A. 32 A/s
    Explanation
    The rate of change of current in a coil is directly proportional to the induced electromotive force (emf) and inversely proportional to the self inductance of the coil. In this case, the emf is given as 8 V and the self inductance is given as 0.25 H. To find the rate of change of current, we can use the formula: rate of change of current = emf / self inductance. Plugging in the given values, we get: rate of change of current = 8 V / 0.25 H = 32 A/s. Therefore, the correct answer is 32 A/s.

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  • 39. 

    The temperature at which velocity of sound in air is two times of its velocity at 10C :

    • A.

      1132 Centigrade

    • B.

      859 Centigrade

    • C.

      658 Centigrade

    • D.

      900 Centigrade

    Correct Answer
    B. 859 Centigrade
    Explanation
    The velocity of sound in air is directly proportional to the square root of temperature. Therefore, if the velocity of sound at 100°C is v, then the velocity of sound at 859°C would be 2v. This is because the square root of 2 is approximately 1.414, so multiplying v by 1.414 gives 2v. Thus, the temperature at which the velocity of sound in air is two times its velocity at 100°C is 859°C.

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  • 40. 

    Ratio of minimum wavelength in Balmer series to that of Pachen series of hydrogen atom is:

    • A.

      4/9

    • B.

      9/4

    • C.

      4

    • D.

      1/9

    Correct Answer
    A. 4/9
    Explanation
    The ratio of the minimum wavelength in the Balmer series to that of the Paschen series of the hydrogen atom is 4/9. This can be explained by the fact that the Balmer series corresponds to the transitions of an electron from higher energy levels to the second energy level, while the Paschen series corresponds to transitions to the third energy level. Since the energy levels increase as we move further away from the nucleus, the transitions to the second energy level (Balmer series) have higher energy and shorter wavelengths compared to transitions to the third energy level (Paschen series). Therefore, the ratio of the minimum wavelength in the Balmer series to that of the Paschen series is 4/9.

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  • 41. 

    In Compton's effect x-rays 1x10-10 m are scattered from carbon z=6 and from zinc z=30.If scattered angle for both is 90 then ratio of their change in wavelength of photon is

    • A.

      6 : 5

    • B.

      1 : 5

    • C.

      1 : 1

    • D.

      1 : 25

    Correct Answer
    A. 6 : 5
    Explanation
    When x-rays are scattered, the change in wavelength of the photon can be calculated using Compton's formula: Δλ = λ' - λ = h / (mec) * (1 - cosθ), where Δλ is the change in wavelength, λ' is the wavelength after scattering, λ is the initial wavelength, h is Planck's constant, me is the electron mass, c is the speed of light, and θ is the scattering angle. Since the scattering angles for carbon and zinc are both 90 degrees, the change in wavelength for both is the same. Therefore, the ratio of their change in wavelength is 1:1. However, the question asks for the ratio of their wavelengths, not the change in wavelength. Since wavelength and change in wavelength are inversely proportional, the ratio of their wavelengths is the inverse of the ratio of their change in wavelength, which is 6:5.

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  • 42. 

    In nuclear reactor control rods are made by:

    • A.

      Boron

    • B.

      Cadmium

    • C.

      Sodium

    • D.

      Either Cadmium or Boron

    Correct Answer
    D. Either Cadmium or Boron
    Explanation
    Control rods are used in nuclear reactors to absorb neutrons and regulate the rate of the nuclear reaction. Both boron and cadmium are effective neutron absorbers and can be used to make control rods. Therefore, the correct answer is either cadmium or boron. Sodium, on the other hand, is not commonly used in control rods as it is not as effective in absorbing neutrons.

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  • 43. 

    Significant figures in 2.00x104 kg are

    • A.

      1

    • B.

      2

    • C.

      3

    • D.

      4

    Correct Answer
    C. 3
    Explanation
    The number 2.00x104 kg has three significant figures. The zeros between the 2 and the 4 are significant because they are sandwiched between two non-zero digits. The zero after the 4 is not significant because it is trailing after a non-zero digit. Therefore, the answer is 3 significant figures.

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  • 44. 

    Body moving along the circumference of a circle completes three revolutions. If the radius of the circular path is 'r'. the ratio of displacement to covered path is:

    • A.

      4πR

    • B.

      6πR

    • C.

      2πR

    • D.

      Zero

    • E.

      None of Given

    Correct Answer
    D. Zero
    Explanation
    The ratio of displacement to covered path is zero. This means that the body ends up at the same position as it started after completing three revolutions along the circumference of the circle. Since the displacement is the change in position, and the body's position remains unchanged, the displacement is zero. Therefore, the ratio of displacement to covered path is zero.

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  • 45. 

    A particle is executing S.H.M has an acceleration as a function of displacement of 64cm/s when it's displacement is 4 cm.Its time period in second is

    • A.

      π/2

    • B.

      π/4

    • C.

      π

    • D.

    • E.

    Correct Answer
    A. π/2
    Explanation
    The given question is asking for the time period of a particle executing simple harmonic motion (S.H.M) when its acceleration is a function of displacement. In S.H.M, the acceleration is directly proportional to the displacement but in the opposite direction. The given information states that when the displacement is 4 cm, the acceleration is 64 cm/s. From this information, we can conclude that the acceleration is maximum at the extreme points of displacement. The time period of S.H.M is the time taken for the particle to complete one full oscillation. Since the acceleration is maximum at the extreme points, the time period will be the time taken for the particle to travel from one extreme point to the other and back. Therefore, the time period is π/2.

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  • 46. 

    Tension in a string is increased by four time. The frequency of the stationary wave becomes?

    • A.

      Same

    • B.

      Increase

    • C.

      Half

    • D.

      Doubled

    Correct Answer
    D. Doubled
    Explanation
    When the tension in a string is increased by four times, the frequency of the stationary wave doubles. This is because the frequency of a wave is directly proportional to the square root of the tension in the string. When the tension is increased by four times, the square root of the tension also increases by two times. Therefore, the frequency of the wave doubles.

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  • 47. 

    Which one is not dependant on superposition principle:

    • A.

      Interference

    • B.

      Diffraction

    • C.

      Beats

    • D.

      Polarization

    Correct Answer
    D. Polarization
    Explanation
    Polarization is not dependent on the superposition principle because it does not involve the interaction or interference of multiple waves. Instead, polarization refers to the orientation of the electric field in a single wave. The superposition principle states that when two or more waves meet, their amplitudes add or subtract, resulting in interference patterns. Interference, diffraction, and beats all involve the superposition of waves, making them dependent on the principle.

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  • 48. 

    In Michelson's rotating experiment the time period of rotation of octagonal mirror is expressed in:

    • A.

      16c/d

    • B.

      16cd

    • C.

      16d/c

    • D.

      D/16c

    Correct Answer
    A. 16c/d
    Explanation
    In Michelson's rotating experiment, the time period of rotation of the octagonal mirror is expressed as 16c/d. This means that the time it takes for the mirror to complete one rotation is equal to 16 times the circumference of the mirror divided by the speed of light. This expression is derived from the experimental setup and the properties of light and mirrors used in the experiment. It helps in understanding the relationship between the rotation of the mirror and the speed of light.

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  • 49. 

    If N is the number of lines per unit length then the grating element is given by:

    • A.

      D=1/2N

    • B.

      D=2N

    • C.

      D=1/N

    • D.

      D=N/2π

    Correct Answer
    C. D=1/N
    Explanation
    The grating element, which represents the distance between adjacent lines on the grating, is given by d=1/N. This means that as the number of lines per unit length (N) increases, the grating element decreases. In other words, the distance between the lines on the grating becomes smaller as the number of lines per unit length increases.

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  • 50. 

    In astronomical telescope intermediate image is:

    • A.

      Real

    • B.

      Inverted

    • C.

      Diminished

    • D.

      All Given

    Correct Answer
    D. All Given
    Explanation
    The intermediate image in an astronomical telescope can be real, inverted, and diminished. In a telescope, the objective lens or mirror forms a real and inverted image of the object being observed. This image is then magnified by the eyepiece, resulting in a final image that is real, inverted, and usually diminished in size. Therefore, all the given options - real, inverted, and diminished - are correct in describing the intermediate image in an astronomical telescope.

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