This question involves refraction. When light travels from glycerin (higher refractive index) to water (lower refractive index), the light wave speeds up as it enters the less dense medium. This increase in speed at the boundary causes the light ray to bend away from the normal. The refracted ray in water makes a larger angle with the normal than the 45° incident angle in glycerin. Choice C incorrectly states the ray bends toward the normal because speed increases, confusing both the bending direction and misunderstanding that speed actually increases when entering a less dense medium. Apply this principle: light entering a less dense medium (lower n) speeds up and bends away from the normal.

This problem tests refraction. When light enters ethanol from air, it moves from a medium with lower refractive index to one with higher refractive index, causing the light wave to slow down. This speed reduction at the boundary makes the light ray bend toward the normal. Even with a small incident angle of 15°, the refracted ray still bends toward the normal, just with a smaller refraction angle. Choice D incorrectly attributes the bending to frequency change, revealing the misconception that frequency varies during refraction when it actually stays constant. The fundamental rule: light entering a denser medium (higher n) slows down and bends toward the normal.

This problem addresses refraction. When light travels from air (lower refractive index) to water (higher refractive index), the light wave slows down as it enters the denser medium. This speed reduction at the boundary causes the light ray to bend toward the normal. The refracted ray in water makes a smaller angle with the normal than the 35° incident angle. Choice C incorrectly states the ray bends away from the normal because speed decreases, revealing confusion about the relationship between speed change and bending direction. To predict refraction: when light enters a denser medium (higher n), it slows down and bends toward the normal.

This question tests refraction. When light exits a high-index crystal and enters air (lower refractive index), the light wave speeds up in the less dense medium. This speed increase at the boundary causes the light ray to bend away from the normal. Even with a small incident angle of 10°, the refracted ray still bends away from the normal, just with a proportionally small increase in angle. Choice D incorrectly suggests frequency decreases, demonstrating the misconception that frequency changes during refraction when it remains constant throughout. The key insight: light exiting a denser medium (higher n) speeds up and bends away from the normal.

This question tests understanding of refraction. When light travels from plastic (higher refractive index) to air (lower refractive index), the light speed increases. As wave fronts cross into air, they speed up, causing the ray to bend away from the normal—like a car wheel leaving sand onto pavement at an angle. Choice D incorrectly claims frequency increases in air, revealing the misconception that frequency changes at boundaries when it actually remains constant. Remember: when light enters a less dense medium, it speeds up and bends away from the normal.

This question tests understanding of refraction. When light travels from a medium with higher refractive index (glass) to one with lower refractive index (air), the light speed increases. As the wave fronts cross the boundary, those entering air first travel faster than those still in glass, causing the ray to bend away from the normal. Choice D incorrectly claims wavelength stays constant—wavelength actually increases in air while frequency remains constant, revealing the misconception that wavelength is conserved across boundaries. Remember: when light enters a less dense medium (lower n), it bends away from the normal.

This question tests understanding of refraction. When light travels from a medium with lower refractive index (air) to one with higher refractive index (glass), the light speed decreases because v = c/n, where n is the refractive index. At the boundary, the component of the wave's velocity parallel to the surface must remain continuous, while the perpendicular component changes due to the speed change. This causes the light ray to bend toward the normal (the line perpendicular to the surface) when entering a denser medium. Choice C incorrectly assumes that constant frequency prevents bending, but frequency conservation doesn't determine ray direction—the speed change does. When light slows down entering a denser medium, always remember it bends toward the normal.

This question tests understanding of refraction. When light travels from a medium with higher refractive index (water) to one with lower refractive index (air), the light speed increases according to $v = c/n$. As the wave crosses the boundary, the parallel component of velocity remains constant while the perpendicular component increases, causing the ray to bend away from the normal. Since the light speeds up in air, the refracted angle becomes larger than the incident angle of $25^\circ$. Choice B incorrectly claims frequency increases, but frequency remains constant across boundaries—only speed and wavelength change. When light speeds up entering a less dense medium, it always bends away from the normal.

This question tests understanding of refraction. When light travels from crown glass (higher refractive index) to air (lower refractive index), the wave speed increases since v = c/n and n_air < n_glass. As the wavefront crosses the boundary, the portion entering air first speeds up relative to the part still in glass, causing the wavefront to rotate away from the normal line. This bending away from the normal always happens when light enters a less dense optical medium. Choice A incorrectly states the speed decreases, showing the misconception that light always slows down at boundaries—actually, speed change depends on relative refractive indices. Remember: when light speeds up (entering lower n media), it bends away from the normal.

This question tests understanding of refraction. When light travels from ethanol (lower refractive index) to acrylic (higher refractive index), the wave speed decreases since v = c/n and n_acrylic > n_ethanol. At the boundary, the leading edge of the wavefront enters the acrylic and slows down while the trailing edge continues at ethanol speed, causing the wavefront to rotate toward the normal. This bending toward the normal characterizes light entering a denser optical medium. Choice D incorrectly claims wavelength stays constant, revealing the misconception that wavelength is preserved during refraction—actually, wavelength changes proportionally with speed while frequency remains constant. Remember: waves bend toward the normal when entering a medium where they slow down.