Physics for Scientists and Engineers, 6e
Chapter 36 – Image Formation
In the overhead view shown here, the image of the stone seen by observer 1 is at C. At which of the five points does observer 2 see the image?
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1. A 2. B 3. C 4. D 5. E
A ray traced from the stone to the mirror and then to observer 2 looks like this:
You are standing about 2 m away from a mirror.
The mirror has water spots on its surface. It’s possible for you to see the water spots and your image both in focus at the same time -
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1. true 2. false
The water spots are 2 m away from you and your image is 4 m away. You cannot focus your eyes on both at the same time.
You wish to reflect sunlight from a mirror onto some paper under a pile of wood in order to start a fire.
Which would be the best choice for the type of mirror?
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1. flat
2. concave 3. convex
A concave mirror will focus the light from a large area of the mirror onto a small area of the paper, resulting in a very high power
input to the paper.
Consider the image in this mirror. Based on the
appearance of this image, you would conclude that
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1. the mirror is concave and the image is real.
2. the mirror is concave and the image is virtual.
3. the mirror is convex and the image is real.
4. the mirror is convex and the image is virtual.
A convex mirror always forms an image with a magnification less than one, so the mirror must be concave. In a
concave mirror, only virtual images are upright. This particular photograph is of the Hubble Space Telescope primary mirror.
In the figure below, what happens to the image point I as the object point O is moved to the right from very far away to very close to the refracting surface?
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1. It is always to the right of the surface.
2. It is always to the left of the surface.
3. It starts off to the left and at some position of O, I
moves to the right of the surface.
4. It starts off to the right and at some position of O, I moves to the left of the surface.
When O is far away, the rays refract into the material of index n2 and converge to form a real image as in Figure 36.18. As O moves very close to the refracting surface, the incident angle of the rays increases so much that rays are no longer refracted back toward the principal axis. This results in a virtual image as shown below:
In this figure, what happens to the image point I as the object point O moves toward the right-hand surface of the material of index of refraction n1?
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1. It always remains between O and the surface, arriving at the surface just as O does.
2. It moves toward the
surface more slowly than O so that eventually O passes I.
3. It approaches the surface and then moves to the right
No matter where O is, the rays refract into the air away from the normal and form a virtual image between O and the surface.
What is the focal length of a pane of window glass?
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1. zero 2. infinity
3. the thickness of the glass 4. impossible to determine
Because the flat surfaces of the plane have
infinite radii of curvature, Equation 36.15 indicates that the focal length is also infinite. Parallel rays striking the plane focus at infinity, which means that they remain parallel after passing through the glass.
Diving masks often have a lens built into the glass for divers who do not have perfect vision. This allows the individual to dive without the necessity for glasses, because the lenses in the faceplate perform the necessary refraction to provide clear vision. The proper design allows the diver to see clearly with the mask on both under water and in the open air. Normal eyeglasses have lenses that are curved on both the front and rear surfaces. The lenses in a diving mask should be curved
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1. only on the front surface 2. only on the rear surface 3. on both the front and
rear surfaces
If there is a curve on the front surface, the refraction will differ at that surface when the
mask is worn in air and water. In order for there to be no difference in refraction (for normal
incidence), the front of the mask should be flat.
A curved mirrored surface can have
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1. spherical aberration but not chromatic aberration 2. chromatic aberration but not spherical aberration 3. both spherical aberration
and chromatic aberration
Because the light reflecting from a mirror does not enter the material of the mirror, there is no opportunity for the dispersion of the material to cause chromatic aberration.
A camera can be modeled as a simple converging lens that focuses an image on the film, acting as the screen. A camera is initially focused on a distant
object. To focus the image of an object close to the camera, the lens must be
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1. moved away from the film.
2. left where it is.
3. moved toward the film.
If the object is brought closer to the lens, the image moves farther away from the lens, behind the plane of the film. In order to bring the image back up to the
film, the lens is moved toward the object and away from the film.
Two campers wish to start a fire during the day. One camper is nearsighted and one is farsighted. Whose glasses should be used to focus the Sun’s rays onto some paper to start the fire?
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1. either camper
2. the nearsighted camper 3. the farsighted camper
The Sun’s rays must converge onto the paper. A farsighted person wears converging lenses.
