# College Physics

Physics & Astronomy

## Quiz 8 : Reflection and Refraction of Light Looking for Introductory Physics Homework Help?

## Quiz 8 :Reflection and Refraction of Light

Question Type  Why does the arc of a rainbow appear with red on top and violet on the bottom
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The phenomena of light involved in the appearance of rainbow with red on top and violet on the bottom are dispersion and refraction of light.
The Sun light comprises of photons of different wavelengths. The different wavelengths of photons are dispersed, when incident on the front surface of raindrop, since the refraction angles are different for different colors. Out of seven colors the red light possesses high wavelength, so it deviates more and violet light possess low wavelength, so it refractive least.
When the light is incident on the rain drop, it gets reflected from the back surface of the drop and again gets refracted from the front end of the drop's surface while leaving the drop. The two lights red and violet emerge outside from the raindrop with different angles. Since, red light deviates most relative to the incident angle, it reaches the observer and the drop appears as red. Similarly, the violet light passes over the observer to appear lower in the sky due to least deviation. Hence, a rainbow appears red on the top and violet on the bottom.

Tags During the Apollo XI Moon landing, a retroreflecting panel was erected on the Moon's surface. The speed of light can be found by measuring the time it takes a laser beam to travel from Earth, reflect from the panel, and return to Earth. If this interval is found to be 2.51 s, what is the measured speed of light Take the center-to-center distance from Earth to the Moon to be 3.84 × 10 8 m. Assume the Moon is directly overhead and do not neglect the sizes of Earth and the Moon.
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The speed of light during its course of travel is defined as the ratio of distance traveled by the light to the time taken. Here, is the distance travelled and is the time taken.
If D is the center to center distance from the Earth to the Moon, is the radius of the Earth, and is the radius of the Moon, then the total distance travelled by the light is, Thus, the speed of the light is, Substitute for D , for , for , and 2.51 s for . Therefore, the speed of the light is .

Tags A ray of light is moving from a material having a high index of refraction into a material with a lower index of refraction. (a) Is the ray bent toward the normal or away from it (b) If the wavelength is 600 nm in the material with the high index of refraction, is it greater, smaller, or the same in the material with the lower index of refraction (c) How does the frequency change as the light moves between the two materials Does it increase, decrease, or remain the same
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Essay

The light rays bend at the interface of the two media, when it transmits from one medium to another medium. The velocity of light is different in different media and the speed of light is more in rarer medium compared with denser medium. Thus, the light deviates from its path, when it travels from one medium to another medium.
The property of the medium, which describes the how light propagates through it is called index of refraction and it is defined as the ratio of speed of light, c in vacuum to the speed of light, v in medium. The index of refraction is inversely proportional to speed of light. So a higher index of refraction means less velocity and a lower index of refraction means higher velocity. Thus, the ray moves from a material in which it travels slowly to a material in which it travels more rapidly, it bends away from the normal. Hence, the light ray is moving from a material of high index of refraction into a material of lower of refraction bends away from the normal.
The relation between speed of light, v and its wavelength, is, Here, is the frequency.
The speed of light is reduced by a factor of index of refraction, when it transmitted from one medium into another medium. Similarly, the wavelength of light also reduces by a factor of index of refraction, since wavelength is directly proportional to speed of light.
Thus, the wavelength of light increases in the lower index of refraction, when light of wavelength, 600 nm moves from the material with a high index of refraction.
The refractive index varies with the wavelength of light, but frequency of light not affected by refractive index. The frequency of the light doesn't change, when it moves from one medium to another medium. Hence, the frequency remains constant , when the light travels between two media.

Tags (a) What is the energy in joules of an x-ray photon with wavelength 1.00 × 10 10 m (b) Convert the energy to electron volts. (c) If more penetrating x-rays are desired, should the wavelength be increased or decreased (d) Should the frequency be increased or decreased
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Tags A light ray travels through three parallel slabs having different indices of refraction as in Figure CQ22.3. The rays shown are only the refracted rays. Rank the materials according to the size of their indices of refraction, from largest to smallest.
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Tags Find the energy of (a) a photon having a frequency of 5.00 × 10 17 Hz and (b) a photon having a wavelength of 3.00 × 10 2 nm. Express your answers in units of electron volts, noting that 1 eV = 1.60 × 10 19 J.
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Tags Under what conditions is a mirage formed On a hot day, what are we seeing when we observe a mirage of a water puddle on the road
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Tags (a) Calculate the wavelength of light in vacuum that has a frequency of 5.45 × 10 14 Hz. (b) What is its wavelength in benzene (c) Calculate the energy of one photon of such light in vacuum. Express the answer in electron volts. (d) Does the energy of the photon change when it enters the benzene Explain.
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Tags Explain why a diamond loses most of its sparkle when submerged in carbon disulfide.
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Tags Find the speed of light in (a) water, (b) crown glass, and (c) diamond.
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Tags A type of mirage called a pingo is often observed in Alaska. Pingos occur when the light from a small hill passes to an observer by a path that takes the light over a body of water warmer than the air. What is seen is the hill and an inverted image directly below it. Explain how these mirages are formed.
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Tags (a) Find a symbolic expression for the wavelength of a photon in terms of its energy E , Planck's constant h , and the speed of light c. (b) What does the equation say about the wavelengths of higher-energy photons
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Tags In dispersive materials, the angle of refraction for a light ray depends on the wavelength of the light. Does the angle of reflection from the surface of the material depend on the wavelength Why or why not
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Tags A ray of light travels from air into another medium, making an angle of 1 = 45.0° with the normal as in Figure P22.7. Find the angle of refraction 2 if the second medium is (a) fused quartz, (b) carbon disulfide, and (c) water.
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Tags The level of water in a clear, colorless glass can easily be observed with the naked eye. The level of liquid helium in a clear glass vessel is extremely difficult to see with the naked eye. Explain. Hint: The index of refraction of liquid helium is close to that of air.
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Tags The two mirrors in Figure P22.8 meet at a right angle. The beam of light in the vertical plane P strikes mirror 1 as shown. (a) Determine the distance the reflected light beam travels before striking mirror 2. (b) In what direction does the light beam travel after being reflected from mirror 2
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Tags Suppose you are told that only two colors of light ( X and Y ) are sent through a glass prism and that X is bent more than Y. Which color travels more slowly in the prism
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Tags An underwater scuba diver sees the Sun at an apparent angle of 45.0° from the vertical. What is the actual direction of the Sun
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