Chapter 29: Light Waves

Interference is a property that occurs when two or more waves overlap and combine to form a new wave pattern. This phenomenon is observed in light waves, sound waves, and water waves. In light waves, interference can result in the formation of bright and dark fringes, as seen in the double-slit experiment. In sound waves, interference can lead to the reinforcement or cancellation of sound depending on the phase relationship between the waves. Similarly, water waves can exhibit interference patterns when two or more waves meet. Therefore, interference is a property that applies to all of these wave types.

The correct answer is "nonsense – you can't polarize a sound wave." This is because sound waves are mechanical waves that propagate through a medium by causing the particles of the medium to vibrate. Polarization is a property of electromagnetic waves, such as light, where the vibrations occur in a specific direction. Since sound waves are not electromagnetic in nature, they cannot be polarized. Therefore, the inventor's proposal to polarize a source of background music and use polarizing earplugs is not feasible.

AM radio waves have longer wavelengths compared to FM radio waves. Longer wavelengths are more likely to diffract or bend around obstacles such as small buildings. Therefore, AM radio waves are diffracted the most around small buildings compared to FM radio waves.

When viewing a soap film with white light coming from almost behind your head, the film acts as a thin layer that reflects and transmits light waves. The colors we perceive are a result of constructive and destructive interference of light waves. Since the angle of incidence and the angle of reflection are different for your friend on the other side of the film, they will likely see a different color due to the variation in the path length of the light waves and the resulting interference pattern.

Dolphins emit sounds of higher frequency to perceive greater detail. Higher frequency sound waves have shorter wavelengths, allowing them to bounce off objects and return to the dolphin's ears more quickly. This enables the dolphin to detect smaller objects and finer details in its surroundings. Lower frequency sounds have longer wavelengths and are better for long-range communication and navigation. Therefore, emitting sounds of higher frequency helps dolphins in their echolocation abilities and enhances their perception of detail.

Polarization is a property that occurs only in transverse waves. In transverse waves, the oscillations of the particles occur perpendicular to the direction of wave propagation. This allows the wave to have a specific orientation or direction of oscillation, which is known as polarization. On the other hand, longitudinal waves have oscillations that occur parallel to the direction of wave propagation, making it impossible for them to exhibit polarization. Therefore, the correct answer is transverse waves.

Polarization is a property of light waves but not of sound waves. Polarization refers to the orientation of the electric field vector in a wave. Light waves can be polarized, meaning their electric field vectors are aligned in a specific direction, whereas sound waves cannot be polarized. Sound waves are longitudinal waves, meaning that the particles of the medium through which they travel oscillate parallel to the direction of the wave, and do not exhibit a specific orientation of the electric field.

When long-wavelength light is seen in the interference colors of a soap bubble, it means that the long-wavelength light is being cancelled out. This cancellation occurs when the thickness of the soap film is equal to an odd multiple of half the wavelength of the light. Since long-wavelength light is being cancelled, it implies that the wavelength being cancelled is relatively short.

Diffraction is a phenomenon that occurs when waves encounter an obstacle or pass through a narrow opening, causing them to spread out and bend around the edges. It is not a result of refraction, reflection, polarization, or dispersion. Interference, on the other hand, is the interaction of waves that results in their reinforcement or cancellation. This interaction can lead to the bending and spreading out of waves, which is characteristic of diffraction. Therefore, interference is the correct answer as it explains the occurrence of diffraction.

Diffraction refers to the bending or spreading of waves as they pass through an opening or around an obstacle. When waves encounter a small opening, the size of the opening is comparable to the wavelength of the wave, resulting in a significant bending or spreading of the waves. On the other hand, when waves encounter a large opening, the size of the opening is much larger than the wavelength, causing less bending or spreading. Therefore, diffraction is more pronounced through relatively small openings.

Polarizing filters in viewing 3-D slides or movies allow each eye to see a different image by blocking out light polarized in the opposite direction. This creates an independent left or right-hand view, which is necessary for the brain to perceive depth and create a stereoscopic effect.

Diffraction refers to the bending of light waves as they pass through a small opening or around an obstacle. In the context of a microscope, diffraction can cause blurring and reduce the clarity of the image, especially when viewing tiny objects. This is because the light waves diffract when they interact with the edges of the specimen, leading to interference patterns and decreased resolution. Therefore, diffraction acts as a hindrance when trying to view tiny objects in a microscope, making it more challenging to observe them with precision.

Double-pane airplane windows that darken when the inner pane is rotated are made possible by the use of thin films. Thin films are layers of material that are only a few nanometers to micrometers thick. In this case, the thin films are likely made of a material that can change its optical properties when subjected to rotation or other external factors. This allows the window to darken or become opaque when needed, providing privacy or reducing glare for passengers.

Monochromatic light refers to light that consists of a single wavelength, which also corresponds to a single frequency and a single color. Therefore, all of these options are correct as they all describe the characteristics of monochromatic light.

The iridescent colors seen in the pearly luster of an abalone shell are due to interference. Interference occurs when light waves interact with each other, either constructively or destructively. In the case of the abalone shell, the layers of the shell act as thin films that reflect and transmit light. When light waves reflect off these layers and interfere with each other, certain wavelengths are reinforced, creating the vibrant and shimmering colors observed in the shell.

When two ideal Polaroids are oriented with their axes parallel to each other, the second Polaroid will only transmit the light that is already polarized by the first Polaroid. Since the first Polaroid transmits 50% of unpolarized light incident on it, the second Polaroid will transmit the same amount of light, which is also 50%. Therefore, when two ideal Polaroids are parallel to each other, 50% of the incident light is transmitted.

The spacing of Newton's rings is determined by the wavelength of light. Red light has a longer wavelength compared to blue or white light. Since the spacing of the rings increases with longer wavelengths, the spacing of Newton's rings will be greater with red light.

The polarization axes of ordinary sunglasses are vertical because they are designed to block horizontally polarized light waves. When light reflects off a flat surface, such as water or a road, it becomes horizontally polarized, causing glare. Ordinary sunglasses have vertical polarization axes that can block this horizontally polarized light, reducing glare and improving visibility.

When plane waves pass through a small opening in a barrier, they tend to spread out or "fan out" on the other side of the opening. This phenomenon is known as diffraction. The diffraction of waves occurs because the opening acts as a secondary source of waves, causing the wavefronts to spread out in all directions. As a result, the waves no longer remain as plane waves but instead exhibit a spreading pattern. Therefore, the correct answer is "fan out."

Diffraction refers to the bending of waves around obstacles or through openings. In the context of radio reception, diffraction plays a helpful role. As radio waves encounter buildings, trees, or other obstacles, they can diffract or bend around them, allowing the signal to reach areas that would otherwise be obstructed. This phenomenon is particularly useful in improving radio reception in urban or hilly areas where line-of-sight transmission may be limited. Therefore, diffraction is beneficial in radio reception.

When the axes of two polaroids are perpendicular to each other, they are in a crossed position. In this configuration, the first polaroid only allows light waves oscillating in one direction to pass through, while the second polaroid only allows light waves oscillating in a perpendicular direction to pass through. As a result, no light can pass through the pair of polaroids when their axes are perpendicular to each other.

The polarization axes of glasses for 3-D viewing are at right angles to each other. This is because 3-D glasses work by presenting a slightly different image to each eye, creating the illusion of depth. Each lens of the glasses is polarized in a different direction, with one lens allowing only vertical light waves to pass through and the other lens allowing only horizontal light waves to pass through. By wearing these glasses, each eye sees a slightly different image, which the brain combines to create the perception of depth. Therefore, the polarization axes of the glasses must be at right angles to each other to achieve this effect.

A hologram is a complex diffraction grating because it is created by recording the interference pattern of light waves. This pattern is then used to recreate a three-dimensional image when illuminated with a coherent light source. The diffraction grating property of a hologram allows it to diffract light in a way that produces a realistic and detailed image. The other options, such as a thin sheet of non-cubic transparent crystals or a pair of semi-crossed polarization filters, do not accurately describe the nature of a hologram.

Newton's rings are a phenomenon that occurs when a convex lens is placed on a flat glass surface, creating a pattern of concentric rings. This pattern is the result of interference between the light waves reflected from the top and bottom surfaces of the lens. The interference causes constructive and destructive interference, resulting in the formation of bright and dark rings. Therefore, the correct answer is interference.

When gasoline forms a thin film on water, the colors observed are a result of interference. Interference occurs when two or more waves interact with each other, either constructively or destructively. In this case, the thin film of gasoline acts as a medium that reflects and transmits light waves. As the light waves reflect off the top and bottom surfaces of the film, they interfere with each other, producing a pattern of colors. This phenomenon is known as thin-film interference and is responsible for the vibrant colors seen on the surface of the gasoline film.

When light passes through an ideal Polaroid filter, half of the light is transmitted and the other half is blocked. However, in the case of a real Polaroid filter, some additional light is absorbed or scattered, resulting in less than half of the light being transmitted. Therefore, the correct answer is "less than half."

Interference colors for light are analogous to beats for sound. Both phenomena involve the combination of two or more waves to produce a new pattern or effect. In the case of interference colors, they are produced when light waves interact and interfere with each other, resulting in the appearance of different colors. Similarly, beats in sound occur when two sound waves of slightly different frequencies combine, creating a periodic variation in the amplitude (loudness) of the resulting sound. Therefore, both interference colors and beats involve the interaction and combination of waves to produce distinct effects.

Camera lenses coated with a layer of transparent material of the right thickness are almost completely non-reflective for light near the middle of the visible spectrum. However, they do reflect a significant amount of red and violet light.

According to Huygens' principle, every point on a wave behaves as a source of new waves. This principle states that each point on a wavefront can be considered as a point source of secondary spherical wavelets. These secondary wavelets combine to form a new wavefront, which explains the phenomenon of diffraction. Therefore, every point on a wave can be seen as a source of new waves.

The interference colors seen in a film of gasoline on a wet street are due to the phenomenon of thin film interference. When light reflects off the top surface of the gasoline film and the bottom surface of the water, it undergoes constructive and destructive interference, resulting in different colors. The water acts as the second reflecting surface in this case, allowing for the interference of light waves and the creation of the observed colors.

Holograms employ both the principles of diffraction and interference. Diffraction refers to the bending or spreading of waves as they pass through an opening or around an obstacle, which is crucial for creating the interference pattern needed for holography. Interference occurs when two or more waves combine and create regions of constructive and destructive interference, resulting in the formation of the holographic image. Therefore, both diffraction and interference are integral to the functioning of holograms.

Waves diffract the most when their wavelength is long. Diffraction occurs when waves encounter an obstacle or pass through a narrow opening, causing them to spread out. The extent of diffraction depends on the wavelength of the waves. Longer wavelengths experience more diffraction because they are able to bend around obstacles or openings more easily than shorter wavelengths. Therefore, when the wavelength is long, the waves will exhibit the highest degree of diffraction.

A thin film appears blue when illuminated with white light because blue light waves have a shorter wavelength and are more likely to undergo destructive interference. This means that the blue light waves cancel each other out, resulting in the perception of the color blue. Therefore, the color being cancelled by destructive interference is not red, green, white, or blue, but rather another color that is not listed as an option.

When viewing a painting with one eye, the brain does not receive depth cues from both eyes, resulting in a flatter perception of the image. With both eyes, the brain can process binocular disparity, which provides depth information and makes the painting appear more three-dimensional. Polaroid glasses do not affect the perception of depth in a painting, as they are used to filter out specific light waves and reduce glare.

The statement suggests that the vibrational direction of the electron and the plane of polarization of the light it emits are aligned or parallel to each other. This means that when the electron vibrates, it emits light that is polarized in the same direction as its vibration.

Non-cubic transparent crystals have a property where light travels through them at different speeds along different optic axes. This means that the speed of light is not the same in all directions within the crystal. This phenomenon is known as birefringence, and it occurs due to the anisotropic nature of these crystals. As a result, light passing through the crystal will experience different refractive indices along different optic axes, causing the light to split into two polarized rays. Therefore, the correct answer is "at different speeds along different optic axes."

The interference colors in a soap bubble indicate that the soap film has two reflecting surfaces. This is because the colors are produced when light waves reflect off both the inner and outer surfaces of the soap film and interfere with each other. The thinness of the soap film also plays a role in the formation of these colors, as the thickness of the film determines the specific wavelengths of light that interfere constructively or destructively. Therefore, both the presence of two reflecting surfaces and the thinness of the soap film contribute to the observed interference colors.

When a hologram is viewed with light that has a longer wavelength than the original light, magnification can be achieved. This is because longer wavelength light has a lower frequency and larger wavefronts, which allows for a larger image to be formed. The diffraction pattern produced by the hologram will have a larger angle, resulting in a magnified image. On the other hand, when viewed with light of shorter wavelength, the diffraction pattern will have a smaller angle, leading to a smaller image. Therefore, the correct answer is that magnification can be accomplished with a hologram when viewed with light that has a longer wavelength than the original light.

The spacing between double-slit interference fringes is determined by the wavelength of the light used and the distance between the slits. When the slits are closer together, the path difference between the waves passing through the slits decreases, resulting in a larger angle of diffraction and wider spacing between the fringes on the screen. Therefore, the correct answer is closer together.

When two Polaroids with their axes aligned are placed together, the second Polaroid will only transmit the light that is already polarized by the first Polaroid. Since the first Polaroid transmits only 40% of incident unpolarized light, the second Polaroid will transmit a percentage of that 40%. Therefore, the overall transmission of light through both Polaroids will be between 0% and 40%.

When exact duplicates of slides are viewed in the left and right positions of a stereo projector, it means that both eyes are seeing the same image simultaneously. In stereoscopic vision, depth perception is created by the slight differences in the images seen by each eye. However, when the images are identical, there are no disparities for the brain to process, resulting in the perception of no depth. Therefore, the correct answer is no depth.

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When polarized light passes through non-cubic transparent crystals, it undergoes a phenomenon called optical rotation. This means that the plane of polarization of the light wave is rotated as it travels through the crystal. This effect is caused by the crystal's molecular structure and can be observed by analyzing the polarization of the transmitted light. Therefore, the correct answer is "is rotated."

Thick films have a greater thickness compared to thin films. When light waves reflect off the bottom surface of a thick film, they travel a longer distance and become more dispersed or spread out. This dispersion causes the waves to be displaced and not align properly to create interference patterns. As a result, the interference effects are less visible in thick films because the waves are too displaced to interfere with each other.