Test Prep
Multiple Choice
16.1 Reflection
In geometric optics, a straight line emerging from a point is called a (an) ________.
- ray
- focal point
- image
- object distance
An image of a 2.0 -cm object reflected from a mirror is 5.0 cm tall. What is the magnification of the mirror?
- 0.4
- 2.5
- 3
- 10
Can a virtual image be projected onto a screen with additional lenses or mirrors? Explain your answer.
- Yes, the rays actually meet behind the lens or mirror.
- No, the image is formed by rays that converge to a point in front of the mirror or lens.
- Yes, any image that can be seen can be manipulated so that it can be projected onto a screen.
- No, the image can only be perceived as being behind the lens or mirror.
16.2 Refraction
What does c represent in the equation ?
- the critical angle
- the refractive index
- the speed of light in a vacuum
- the speed of light in a transparent material
What is the term for the minimum angle at which a light ray is reflected back into a material and cannot pass into the surrounding medium?
- critical angle
- incident angle
- angle of refraction
- angle of reflection
Consider these indices of refraction: glass: 1.52, air: 1.0003, water: 1.333. Put these materials in order from the one in which the speed of light is fastest to the one in which it is slowest.
- The speed of light in water > the speed of light in air > the speed of light in glass.
- The speed of light in glass > the speed of light in water > the speed of light in air.
- The speed of light in air > the speed of light in water > the speed of light in glass.
- The speed of light in glass > the speed of light in air > the speed of light in water.
- Because of the refraction of light, the light coming from the object bends toward the normal at the interface of water and air. This causes the object to appear at a location that is above the actual position of the object. Hence, the image appears to be at a depth that is more shallow than the actual depth.
- Because of the refraction of light, the light coming from the object bends away from the normal at the interface of water and air. This causes the object to appear at a location that is above the actual position of the object. Hence, the image appears to be at a depth that is more shallow than the actual depth.
- Because of the refraction of light, the light coming from the object bends toward the normal at the interface of water and air. This causes the object to appear at a location that is below the actual position of the object. Hence, the image appears to be at a depth that is more shallow than the actual depth.
- Because of the refraction of light, the light coming from the object bends away from the normal at the interface of water and air. This causes the object to appear at a location that is below the actual position of the object. Hence, the image appears to be at a depth that is more shallow than the actual depth.
16.3 Lenses
For a given lens, what is the height of the image divided by the height of the object () equal to?
- power
- focal length
- magnification
- radius of curvature
Which part of the eye has the greatest density of light receptors?
- the lens
- the fovea
- the optic nerve
- the vitreous humor
What is the power of a lens with a focal length of 10 cm?
- 10 m–1, or 10 D
- 10 cm–1, or 10 D
- 10 m, or 10 D
- 10 cm, or 10 D
- Chromatic aberration results from the dependence of the frequency of light on the refractive index, which causes dispersion of different colors of light by a lens so that each color has a different focal point.
- Chromatic aberration results from the dispersion of different wavelengths of light by a curved mirror so that each color has a different focal point.
- Chromatic aberration results from the dependence of the reflection angle at a spherical mirror’s surface on the distance of light rays from the principal axis so that different colors have different focal points.
- Chromatic aberration results from the dependence of the wavelength of light on the refractive index, which causes dispersion of different colors of light by a lens so that each color has a different focal point.
Short Answer
16.1 Reflection
Distinguish between reflection and refraction in terms of how a light ray changes when it meets the interface between two media.
- Reflected light penetrates the surface whereas refracted light is bent as it travels from one medium to the other.
- Reflected light penetrates the surface whereas refracted light travels along a curved path.
- Reflected light bounces from the surface whereas refracted light travels along a curved path.
- Reflected light bounces from the surface whereas refracted light is bent as it travels from one medium to the other.
- Light passing through air is partially reflected and refracted when it meets a glass surface. It is reflected because glass has a smooth surface; it is refracted while passing into the transparent glass.
- Light passing through air is partially reflected and refracted when it meets a glass surface. It is reflected because glass has a rough surface, and it is refracted while passing into the opaque glass.
- Light passing through air is partially reflected and refracted when it meets a glass surface. It is reflected because glass has a smooth surface; it is refracted while passing into the opaque glass.
- Light passing through air is partially reflected and refracted when it meets a glass surface. It is reflected because glass has a rough surface; it is refracted while passing into the transparent glass.
A concave mirror has a focal length of 5.00 cm. What is the image distance of an object placed 7.00 cm from the center of the mirror?
- −17.5 cm
- −2.92 cm
- 2.92 cm
- 17.5 cm
An 8.0 -cm tall object is placed 6.0 cm from a concave mirror with a magnification of –2.0. What are the image height and the image distance?
- hi = – 16 cm, di = – 12 cm
- hi = – 16 cm, di = 12 cm
- hi = 16 cm, di = – 12 cm
- hi = 16 cm, di = 12 cm
16.2 Refraction
Water floats on a liquid called carbon tetrachloride. The two liquids do not mix. A light ray passing from water into carbon tetrachloride has an incident angle of 45.0° and an angle of refraction of 40.1°. If the index of refraction of water is 1.33, what is the index of refraction of carbon tetrachloride?
- 1.60
- 1.49
- 1.21
- 1.46
Describe what happens to a light ray when it is refracted. Include in your explanation comparison of angles, comparison of refractive indices, and the term normal.
- When a ray of light goes from one medium to another medium with a different refractive index, the ray changes its path as a result of interference. The angle between the ray and the normal (the line perpendicular to the surfaces of the two media) is greater in the medium with the greater refractive index.
- When a ray of light goes from one medium to another medium with a different refractive index, the ray changes its path as a result of refraction. The angle between the ray and the normal (the line perpendicular to the surfaces of the two media) is less in the medium with the greater refractive index.
- When a ray of light goes from one medium to another medium with a different refractive index, the ray does not change its path. The angle between the ray and the normal (the line parallel to the surfaces of the two media) is the same in both media.
- When a ray of light goes from one medium to another medium with a different refractive index, the ray changes its path as a result of refraction. The angle between the ray and the normal (the line perpendicular to the surfaces of the two media) is less in the medium with the lower refractive index.
16.3 Lenses
What are two equivalent terms for a lens that always causes light rays to bend away from the principal axis?
- a diverging lens or a convex lens
- a diverging lens or a concave lens
- a converging lens or a concave lens
- a converging lens or a convex lens
Define the term virtual image.
- A virtual image is an image that cannot be projected onto a screen.
- A virtual image is an image that can be projected onto a screen.
- A virtual image is an image that is formed on the opposite side of the lens from where the object is placed.
- A virtual image is an image that is always bigger than the object.
- The eyes of a nearsighted person have focal points beyond the retina. A farsighted person has eyes with focal points between the lens and the retina.
- A nearsighted person has eyes with focal points between the lens and the retina. A farsighted person has eyes with focal points beyond the retina.
- A nearsighted person has eyes with focal points between the lens and the choroid. A farsighted person has eyes with focal points beyond the choroid.
- A nearsighted person has eyes with focal points between the lens and the retina. A farsighted person has eyes with focal points on the retina.
- A converging lens disperses the rays so they focus on the retina.
- A converging lens bends the rays closer together so they do not focus on the retina.
- A converging lens bends the rays closer together so they focus on the retina.
- A converging lens disperses the rays so they do not focus on the retina.
What is the magnification of a lens if it produces a 12-cm-high image of a 4 -cm -high object? The image is virtual and erect.
Extended Response
16.1 Reflection
- The bulb is at the center of curvature of the small mirror and at the focal point of the large mirror.
- The bulb is at the focal point of the small mirror and at the focal point of the large mirror.
- The bulb is at the center of curvature of the small mirror and at the center of curvature of the large mirror.
- The bulb is at the focal point of the small mirror and at the center of curvature of the large mirror.
16.2 Refraction
Describe total internal reflection. Include a definition of the critical angle and how it is related to total internal reflection. Also, compare the indices of refraction of the interior material and the surrounding material.
- When the interior material has a smaller index of refraction than the surrounding material, the incident ray may approach the boundary at an angle (called the critical angle) such that the refraction angle is 90° . The refracted ray cannot leave the interior, so it is reflected back inside and total internal reflection occurs.
- When the interior material has a smaller index of refraction than the surrounding material, the incident ray may approach the boundary at an angle (called the critical angle) such that the refraction angle is less than 90° . The refracted ray cannot leave the interior, so it is reflected back inside and total internal reflection occurs.
- When the interior material has the same index of refraction as the surrounding material, the incident ray approaches the boundary at an angle (called the critical angle) such that the refraction angle is less than 90° . The refracted ray cannot leave the interior, so it is reflected back inside and total internal reflection occurs.
- When the interior material has a greater index of refraction than the surrounding material, the incident ray may approach the boundary at an angle (called the critical angle) such that the refraction angle is 90° . The refracted ray cannot leave the interior, so it is reflected back inside and total internal reflection occurs.
16.3 Lenses
The muscles that change the shape of the lens in the eyes have become weak, causing vision problems for a person. In particular, the muscles cannot pull hard enough on the edges of the lens to make it less convex.
Part A—What condition does inability cause?
Part B—Where are images focused with respect to the retina?
Part C—Which type of lens corrects this person’s problem? Explain.
- Part A—This condition causes hyperopia.
Part B—Images are focused between the lens and the retina.
Part C—A converging lens gathers the rays slightly so they focus onto the retina.
- Part A—This condition causes myopia.
Part B—Images are focused between the lens and the retina.
Part C—A converging lens gathers the rays slightly so they focus onto the retina.
- Part A—This condition causes hyperopia.
Part B—Images are focused between the lens and the retina.
Part C—A diverging lens spreads the rays slightly so they focus onto the retina.
- Part A—This condition causes myopia.
Part B—Images are focused between the lens and the retina.
Part C—A diverging lens spreads the rays slightly so they focus onto the retina.