Online Physics Quiz 2020 For B. Sc. Sem IV Organized By Department Of Physics, Kamla Nehru Mahavidyalaya, NaGPur

The correct answer is "a = b = c, α = β = γ = 900". This answer indicates that all three axes (a, b, and c) have equal lengths, and all three angles (α, β, and γ) are 90 degrees. This is characteristic of a cubic crystal system, where the crystal structure has a cubic symmetry. In this system, the crystal lattice is formed by repeating units in a cubic arrangement, with equal dimensions in all directions.

Wilhelm Rontgen is credited with the invention of X-rays. In 1895, Rontgen accidentally discovered X-rays while experimenting with cathode rays. He noticed that a fluorescent screen in his lab started to glow even though it was not directly exposed to the cathode rays. Rontgen further investigated this phenomenon and named the newly discovered rays "X-rays". He published his findings and conducted extensive research on X-rays, which led to their widespread use in medical imaging and other fields. Therefore, Wilhelm Rontgen is the correct answer for the inventor of X-rays.

Satellites rely on solar cells as their source of energy. Solar cells, also known as photovoltaic cells, convert sunlight directly into electricity. This is a practical and efficient method for powering satellites as they are exposed to sunlight while orbiting the Earth. Solar cells are lightweight, durable, and can generate electricity for extended periods, making them ideal for powering satellites in space. Fuel cells, Edison cells, and cryogenic storage are not commonly used as energy sources for satellites.

In a face-centered cubic (FCC) structure, each corner of the cube is shared by 8 unit cells, while each face is shared by 2 unit cells. Therefore, each unit cell contains 1/8th of an atom from each corner (8 corners x 1/8th = 1 atom) and 1/2 of an atom from each face (6 faces x 1/2 = 3 atoms). Adding these together gives a total of 4 atoms per unit cell in an FCC structure.

The letter 'h' in the given equation stands for Planck's constant. Planck's constant is a fundamental constant in quantum mechanics that relates the energy of a photon to its frequency. It is denoted by the symbol 'h' and has a value of approximately 6.626 x 10^-34 joule-seconds.

X-rays travel in a straight line in free space because they are electromagnetic waves. Electromagnetic waves, including X-rays, propagate in a straight line unless they encounter an obstacle or are deflected by a medium. This straight line propagation is due to the nature of electromagnetic waves, which consist of oscillating electric and magnetic fields that move perpendicular to each other and the direction of wave propagation. Therefore, X-rays do not exhibit periodic oscillations, non-periodic oscillations, or zig-zag paths, but instead travel in a straight line.

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The cathode in the Coolidge tube is made of tungsten. Tungsten is commonly used in cathodes because it has a high melting point, good electron emission properties, and can withstand high temperatures. It is an ideal material for cathodes in X-ray tubes as it can generate a large number of electrons when heated, which are then accelerated towards the anode to produce X-rays. Quartz, iron, and barium are not typically used as cathode materials in Coolidge tubes.

The process described in the question refers to the movement of atoms from a lower energy level to a higher energy level. This process is commonly known as "pumping." The other options mentioned, such as assembling, gathering, and gearing, do not accurately describe the process of raising atoms to higher energy levels.

The smallest portion of the lattice is known as the unit cell. It is a repeating unit that represents the entire lattice structure. The unit cell contains one or more lattice points and possesses the same symmetry as the overall lattice. It is used to describe the arrangement of atoms or ions in a crystal lattice and is essential in understanding the properties and behavior of materials.

The coordination number for an ideal BCC metallic crystal is 8. In a BCC structure, each atom is surrounded by 8 neighboring atoms, forming a cube-like arrangement. This means that each atom has 8 nearest neighbors, resulting in a coordination number of 8.

X-ray crystallography uses Bragg's law for its implementation. Bragg's law describes the relationship between the angles at which X-rays are diffracted by a crystal lattice and the spacing between the crystal planes. This law allows scientists to analyze the diffraction pattern produced by X-rays passing through a crystal and determine the arrangement of atoms within the crystal. By measuring the angles and intensities of the diffracted X-rays, valuable information about the structure and composition of the crystal can be obtained.

The base terminal does not belong to the MOSFET. The MOSFET is a type of transistor that has three terminals: the source, gate, and drain. The base terminal is typically associated with a different type of transistor called a bipolar junction transistor (BJT). In a MOSFET, the gate terminal is used to control the flow of current between the source and drain terminals. Thus, the base terminal is not part of the MOSFET.

The correct answer is "Light Amplification by Stimulated Emission of Radiation." LASER is an acronym that stands for Light Amplification by Stimulated Emission of Radiation. This term describes the process by which a laser device produces a highly focused and intense beam of light. In this process, the light is amplified through stimulated emission, where photons are emitted in phase with the incident photons, resulting in a coherent and concentrated beam of light.

The Raman effect is the scattering of photons. When light interacts with a material, some of the photons can undergo a change in energy and wavelength. This change is caused by the interaction between the photons and the vibrational or rotational modes of the material's molecules. This phenomenon, known as the Raman effect, provides valuable information about the molecular structure and dynamics of the material being studied.

A metastable state refers to a longer-lived upper energy level in an atom where the atom remains excited for a significant amount of time. Unlike stable states, which quickly transition to lower energy levels, metastable states have a longer lifetime before returning to their ground state. This is due to certain restrictions or barriers that prevent the atom from easily transitioning to a lower energy level. As a result, atoms in a metastable state can retain their excited state for an appreciable period, making it an accurate description for the given scenario.

The total angular quantum number (J) is given by adding the orbital quantum number (L) and the spin quantum number (S). This is because the total angular momentum of an atom or particle is the sum of the orbital angular momentum and the spin angular momentum. Therefore, the correct answer is J = L + S.

The different types of energies associated with a molecule include electronic energy, vibrational energy, and rotational energy. Electronic energy refers to the energy associated with the movement of electrons within the molecule. Vibrational energy is the energy associated with the vibration of the atoms within the molecule. Rotational energy is the energy associated with the rotation of the molecule as a whole. Therefore, all of these energies are associated with a molecule.

The LED should be forward biased in order to allow current to flow through it and emit light. In forward bias, the positive terminal of the power supply is connected to the anode of the LED, while the negative terminal is connected to the cathode. This allows the electrons and holes to recombine at the junction, releasing energy in the form of light. Reverse biasing, on the other hand, prevents current flow and does not allow the LED to emit light. No biasing is required means that the LED will not work without any external voltage applied.

5-fold symmetry is not possible with respect to rotational symmetry operations. This is because a 5-fold symmetry requires dividing a circle into 5 equal parts, which cannot be achieved with any combination of rotations. In rotational symmetry, an object should be able to be rotated by a certain angle and still remain unchanged. However, no angle of rotation can divide a circle into 5 equal parts, making 5-fold symmetry impossible.

The correct answer is "Unipolar." A JFET (Junction Field Effect Transistor) is called a unipolar transistor because its operation is based on the movement of majority charge carriers (either electrons or holes) in a single type of semiconductor material. Unlike bipolar transistors that rely on the movement of both majority and minority charge carriers, JFETs only use one type of charge carrier for their operation.

The given equation eV = hnmax represents the Duane-Hunt rule. This equation relates the energy of an electron (eV) to the maximum frequency of light radiation (nmax). It states that the product of the electron charge (e) and the applied voltage (V) is equal to the product of Planck's constant (h) and the maximum frequency of light radiation (nmax). This equation is used to calculate the energy of electrons in a system when the maximum frequency of light radiation is known.

A JFET (Junction Field-Effect Transistor) has high input impedance, meaning that it does not draw much current from the input source, allowing for efficient signal transfer. Additionally, JFETs have low noise levels, meaning that they introduce minimal unwanted electrical signals or interference into the circuit. These advantages make JFETs suitable for applications requiring high sensitivity and low signal distortion, such as in amplifiers or audio equipment.

Coherence is a unique property of LASER. Coherence refers to the ability of the light waves emitted by a LASER to maintain a constant phase relationship with each other. This means that the waves are in sync and have a consistent pattern, resulting in a highly focused and concentrated beam of light. Coherence is essential for the laser's ability to produce a narrow beam that can travel long distances without spreading out. This property allows lasers to be used in various applications such as telecommunications, medicine, and manufacturing.

The given equation, IE = IC + IB, represents the relationship between the emitter current (IE), collector current (IC), and base current (IB) in a transistor. This equation shows that the total emitter current is equal to the sum of the collector current and base current. It is a fundamental equation in transistor analysis and is used to understand the behavior and characteristics of transistors in electronic circuits.

Quantum Theory is the correct answer because it provides a satisfactory explanation for the Raman effect. The Raman effect refers to the inelastic scattering of light, where the scattered light undergoes a change in wavelength. This phenomenon can be explained by the interaction between light and the vibrational modes of molecules. Quantum Theory accurately describes the behavior of particles and their interactions, including the interaction between photons and molecules in the Raman effect. Classical Theory and Langevin Theory do not provide a satisfactory explanation for this phenomenon.

The He-Ne laser is a gas laser because it uses a mixture of helium and neon gas as the active medium. Gas lasers work by exciting the gas atoms or molecules to higher energy levels, which then emit light when they return to their ground state. In the case of the He-Ne laser, the helium-neon gas mixture is excited by an electrical discharge, and it emits a red laser light with a wavelength of 632.8 nanometers.

The relation between wavelength, frequency, and velocity of a wave is given by the equation: wavelength = velocity / frequency. This equation states that the wavelength of a wave is inversely proportional to its frequency and directly proportional to its velocity. In other words, as the frequency of a wave increases, its wavelength decreases, and vice versa. Additionally, as the velocity of a wave increases, its wavelength also increases. This equation is fundamental in understanding the behavior and characteristics of waves in various contexts such as light, sound, and electromagnetic waves.

The Raman effect is analogous to the Compton effect. Both effects involve the interaction of photons with matter. In the Raman effect, a photon is scattered by a molecule, resulting in a change in its energy and wavelength. Similarly, in the Compton effect, a photon interacts with an electron, causing it to recoil and resulting in a change in the photon's energy and wavelength. Both effects provide valuable information about the nature of matter and have been extensively studied in the field of quantum mechanics.

X-ray crystallography uses the characteristic of diffraction to study the structure of crystals. When X-rays pass through a crystal, they interact with the atoms in the crystal lattice, causing the X-rays to diffract or scatter. By measuring the angles and intensities of the diffracted X-rays, scientists can determine the arrangement of atoms within the crystal and obtain valuable information about its structure. Diffraction is a fundamental property of light that allows X-ray crystallography to provide detailed insights into the atomic and molecular structures of various materials.

The base of a transistor is lightly doped. This is because the base region is responsible for controlling the flow of current between the emitter and collector regions. By lightly doping the base, the transistor can achieve a higher gain and better control over the current flow. Additionally, the lightly doped base helps to minimize the recombination of charge carriers, improving the overall efficiency of the transistor.

The wave number corresponding to a particular energy state is given by the equation that relates the energy of a photon to its wavelength. This equation is known as the Planck-Einstein relation, which states that the energy of a photon is equal to Planck's constant (h) multiplied by the speed of light (c), divided by the wavelength of the photon. Therefore, the wave number (k) can be calculated by dividing the energy of the photon by Planck's constant.

Bragg's X-ray spectrometer is not used to identify the physical properties of liquids because liquids do not have a regular and ordered atomic structure like solids. X-ray spectrometry relies on the diffraction of X-rays by the crystal lattice of a material to determine its physical properties. Liquids do not have a fixed arrangement of atoms and therefore do not produce the characteristic diffraction pattern that can be analyzed by the spectrometer.

In computer printers, semiconductor lasers are commonly used. Semiconductor lasers are compact and efficient, making them suitable for use in small devices like printers. They are also capable of producing high-quality prints with precise and sharp details. Additionally, semiconductor lasers can be easily modulated, allowing for faster printing speeds. Overall, semiconductor lasers are a popular choice for computer printers due to their size, efficiency, and printing capabilities.

A chemical compound of N atoms has 3 degrees of freedom for each atom, which accounts for the translational, rotational, and vibrational motion. Since there are N atoms, the total number of degrees of freedom is 3N.

Moseley's Law states that the frequency of a given characteristic X-ray line increases regularly with the increase in atomic number of the element. This means that as the atomic number of an element increases, the frequency of its characteristic X-ray line also increases. Therefore, the correct answer is "Increases".

The band gap energy of silicon semiconductor is 1.1 eV. The band gap energy refers to the energy difference between the valence band and the conduction band in a semiconductor material. It determines the energy required for an electron to move from the valence band to the conduction band, thus allowing the material to conduct electricity. In the case of silicon, the band gap energy of 1.1 eV indicates that it is a moderate semiconductor, neither a good conductor nor a good insulator.

For an n-channel FET, the direction of current flow is from the drain terminal to the source terminal. This is because in an n-channel FET, the channel is formed by the flow of electrons from the source to the drain when a positive voltage is applied to the gate terminal. Therefore, the current flows in the opposite direction, from the drain to the source.

The moment of inertia of a polyatomic molecule is greater than that of a diatomic molecule. This is because a polyatomic molecule consists of three or more atoms, which are distributed in space and can rotate around multiple axes. This distribution of mass results in a larger moment of inertia compared to a diatomic molecule, which consists of only two atoms and has a simpler rotational motion.

Raman spectra occur due to changes in the molecular states. Raman spectroscopy is a technique that involves the interaction of light with molecules, causing the molecules to undergo vibrational or rotational changes. These changes in molecular states result in the Raman spectra, which provide information about the molecular structure and composition. Atomic states alone do not contribute to Raman spectra, as Raman scattering primarily involves the interaction of light with molecular vibrations. Therefore, the correct answer is the molecular states.

The Miller indices (223) represent a plane that intersects the X-axis at 2/3 of the unit cell length, the Y-axis at 2/2 or the full unit cell length, and the Z-axis at 3/2 of the unit cell length. This can be visualized as a plane that cuts through the unit cell at specific fractional coordinates along each axis.

The main application of the enhancement mode MOSFET is switching. Enhancement mode MOSFETs are designed to operate in the "on" or "off" state, making them ideal for switching applications where a signal needs to be turned on or off rapidly. They have a high input impedance and low output impedance, allowing them to efficiently control the flow of current. This makes them suitable for applications such as power supplies, motor control, and digital logic circuits where fast switching is required.

The Raman spectrum is said to consist of Stokes lines when there is a positive shift in the frequency (Δv > 0). Stokes lines occur when the scattered light has less energy than the incident light, indicating that the molecule has gained energy from the interaction with the incident light. This shift in frequency is known as the Raman shift and is a characteristic feature of the Raman spectrum.

Each point in a reciprocal lattice corresponds to a particular set of parallel planes of the direct lattice. The reciprocal lattice is a mathematical construct that is used to describe the periodicity of a crystal lattice in reciprocal space. The points in the reciprocal lattice are related to the planes in the direct lattice through the reciprocal lattice vector. These planes in the direct lattice are parallel to each other and are represented by the points in the reciprocal lattice. Therefore, the correct answer is "A particular set of parallel planes of the direct lattice."

A light emitting diode is heavily doped because it is designed to emit light when current passes through it. Doping refers to the process of intentionally adding impurities to a semiconductor material to modify its electrical properties. In the case of a LED, the semiconductor material is heavily doped with impurities to create a p-n junction, which allows the LED to emit light when forward biased.

A heat sink is a device that helps dissipate heat generated by a transistor, thereby improving its thermal stability. When a transistor operates, it generates heat due to the flow of current. If this heat is not properly dissipated, it can cause the transistor to overheat, leading to a decrease in performance and potentially damaging the device. By using a heat sink, the excess heat is transferred away from the transistor, allowing it to operate at a lower temperature and improving its stability.

The Born-Oppenheimer approximation states that the electronic and nuclear motions in a molecule can be treated separately. This means that the electrons move much faster than the nuclei, so the statement "The electrons in a molecule move much faster than the nuclei" is a correct aspect of the Born-Oppenheimer approximation. Additionally, the approximation assumes that the electronic and vibrational motions of a molecule are approximately separable, meaning they can be treated independently. It also states that the electronic energy curves serve as potential energy functions for nuclear vibrational motion. However, the statement "Excited electronic states have the same equilibrium internuclear distance as the ground electronic state" is not a correct aspect of the Born-Oppenheimer approximation.

X-rays lie in the region of the electromagnetic spectrum ranging from 10 Å to 0.01 Å. This range is known as the X-ray region, which has shorter wavelengths and higher energy than visible light. X-rays are used in various fields such as medicine, industry, and research for their ability to penetrate through objects and provide detailed images.

The Laue method of diffraction uses X-rays of continuous type. In this method, a crystal is placed in the path of an X-ray beam and the resulting diffraction pattern is observed. The continuous type X-rays used in this method have a wide range of wavelengths, allowing for a more detailed analysis of the crystal structure. The rotating crystal and powder methods, on the other hand, use monochromatic X-rays, which have a single wavelength. Therefore, the correct answer is Laue.

The gate voltage in a JFET at which drain current becomes zero is called the cut-off voltage. At this voltage, the JFET is in a non-conducting state, and the channel between the source and drain is completely closed off. This prevents any current from flowing through the device, resulting in a drain current of zero.