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_Multiple
Choice

The
relative index of refraction between two media is 1.20. Compared to
the velocity of light in medium 1, the velocity of light in medium 2
will be

greater
by 1.2 times

reduced
by 1.2 times

the
same

The
velocity will depend on the two media.

The
velocity will depend on the angle of incidence.

What
is the approximate angle of refraction for a ray of light incident
from air on a piece of quartz at a 37° angle?

24°
37°
42°
66°
75°

Which
material will produce a converging lens with the longest focal
length?

Lucite

Crown
glass

Flint
glass

Quartz

Diamond

An
object is placed in front of a converging lens in such a way that
the image produced is inverted and larger. If the lens were replaced
by one with a larger index of refraction, the size of the image
would

increase

decrease

increase
or decrease, depending on the degree of change

remain
the same

increase
or decrease depending on the wavelength of the light

You
wish to make an enlarged reproduction of a document using a copying
machine. When you push the enlargement button, the lens inside the
machine moves to a point

equal
to f

equal
to 2f

between
f and 2f

beyond
2f

less
than f

A
negative image distance means that the image formed by a concave
mirror will be
real

erect

inverted

smaller

both
(b) and (d)

Real
images are always produced by

plane
mirrors

convex
mirrors

concave
lenses

convex
lenses

both
(b) and (d)

The
focal length of a convex mirror with a radius of curvature of 8 cm
is

4
cm

4
cm

8
cm

8
cm

16
cm

An
object is located 15 cm in front of a converging lens. An image
twice as large as the object appears on the other side of the lens.
The image distance must be

15
cm

30
cm

45
cm

60
cm

75
cm

A
1.6metertall person stands 1.5 m in front of a vertical plane
mirror. The height of her image is

0.8
cm

2.6
cm

3.2
cm

4.5
cm

1.6
cm

Immersion
oil is a transparent liquid used in microscopy. It has an absolute
index of refraction equal to 1.515. A glass rod attached to the cap
of a bottle of immersion oil is practically invisible when viewed at
certain angles (under normal lighting conditions). Explain how this
might occur.

Explain
why a diamond sparkles more than a piece of glass of similar size
and shape.

Explain
why total internal reflection occurs at boundaries between
transparent media for which the relative index of refraction is less
than 1.0.

Why
do passengerside mirrors on cars have a warning that states:
Objects are closer than they appear?

Two
lenses have identical sizes and shapes. One is made from quartz
(n=1.46), and the other is made from class (n=1.5). Which lens would
make a better magnifying class? Explain.

Why
do lenses produce chromatic aberration whereas spherical mirrors do
not?
Answers
_Multiple Choice Answers
(B) The velocity relationship is given by the formula v1/v2=n2/n1. Since the relative index of refraction is defined to be equal to the ration n2/n1, we see that v1=1.2(v2). Thus, compared to v1, v2 is reduced by 1.2 times.
(A) Snell’s law in air is given by sini/sinr=n2. The absolute index of refraction for quartz is 1.46. Substitution yields a value of 24 degrees for the angle of refraction.
(D) The longest focal length will be produced by the material that refracts the least, that is, has the smallest index of refraction. Of the five choices, quartz has the lowest index of refraction.
(B) The lens formula can be rewritten as di=do/(dof). If the object remains in the same position relative to the lens, then using a larger index of refraction will imply a smaller focal length. The image will move closer to the lens and consequently will be smaller.
(C) To produce an enlarged real image, the object must be located between f and 2f.
(B) In a concave mirror, a negative image distance implies a virtual image, which is enlarged and erect.
(D) Only a convex lens or a concave mirror can produce a real image.
(B) The radius of curvature of a spherical mirror is twice the focal length. However, in a convex mirror, the focal length is taken to be negative.
(B) The equation governing magnification in a conerging lens is m=di/do. After substituting the variables, di=30cm.
(E) A plane mirror produces a virtual image that is the same size as the object in all cases.
Free Response Answers
1. The index of refraction for the glass is very nearly equal to that for the immersion oil. When the applicator rod is filled with liquid, the light passes through both media without refracting and makes the glass rod appear invisible.
2. A diamond has a lower critical angle of incidence than glass.Therefore, when turned through various angles, the light passing through a diamond is internally reflected and then dispersed more easily than through glass. This creates the "sparkling" effect.
3. In order to produce total internal reflection, the angle of refraction must exceed 90 degrees. This is possible only when light passes from a high index material to one with a low index of refraction. Under these conditions, the relative index of refraction for the two media is less than 1.0.
4. Passenger side mirrors are convex in shape. This distorts images because of the divergence of the light, making them appear to be smaller and more distant than they actually are.
5. Using the lens construction diagrams, we see that for case V the lens becomes a magnifying glass. Changing the focal length affects the size and location of the image. If the focal length is decreased, the image size and distance will increase. A shorter focal length is obtained by using a material with a higher index of refraction. Hence, glass would make a better magnifying glass.
6. Chromatic aberration is due to the dispersion of white light into the colors of the spectrum. Since a mirror does not disperse light on reflection, this problem does not occur. This observation was the motivation for Sir Isaac Newton to invent the reflecting telescope in 1671.
(B) The velocity relationship is given by the formula v1/v2=n2/n1. Since the relative index of refraction is defined to be equal to the ration n2/n1, we see that v1=1.2(v2). Thus, compared to v1, v2 is reduced by 1.2 times.
(A) Snell’s law in air is given by sini/sinr=n2. The absolute index of refraction for quartz is 1.46. Substitution yields a value of 24 degrees for the angle of refraction.
(D) The longest focal length will be produced by the material that refracts the least, that is, has the smallest index of refraction. Of the five choices, quartz has the lowest index of refraction.
(B) The lens formula can be rewritten as di=do/(dof). If the object remains in the same position relative to the lens, then using a larger index of refraction will imply a smaller focal length. The image will move closer to the lens and consequently will be smaller.
(C) To produce an enlarged real image, the object must be located between f and 2f.
(B) In a concave mirror, a negative image distance implies a virtual image, which is enlarged and erect.
(D) Only a convex lens or a concave mirror can produce a real image.
(B) The radius of curvature of a spherical mirror is twice the focal length. However, in a convex mirror, the focal length is taken to be negative.
(B) The equation governing magnification in a conerging lens is m=di/do. After substituting the variables, di=30cm.
(E) A plane mirror produces a virtual image that is the same size as the object in all cases.
Free Response Answers
1. The index of refraction for the glass is very nearly equal to that for the immersion oil. When the applicator rod is filled with liquid, the light passes through both media without refracting and makes the glass rod appear invisible.
2. A diamond has a lower critical angle of incidence than glass.Therefore, when turned through various angles, the light passing through a diamond is internally reflected and then dispersed more easily than through glass. This creates the "sparkling" effect.
3. In order to produce total internal reflection, the angle of refraction must exceed 90 degrees. This is possible only when light passes from a high index material to one with a low index of refraction. Under these conditions, the relative index of refraction for the two media is less than 1.0.
4. Passenger side mirrors are convex in shape. This distorts images because of the divergence of the light, making them appear to be smaller and more distant than they actually are.
5. Using the lens construction diagrams, we see that for case V the lens becomes a magnifying glass. Changing the focal length affects the size and location of the image. If the focal length is decreased, the image size and distance will increase. A shorter focal length is obtained by using a material with a higher index of refraction. Hence, glass would make a better magnifying glass.
6. Chromatic aberration is due to the dispersion of white light into the colors of the spectrum. Since a mirror does not disperse light on reflection, this problem does not occur. This observation was the motivation for Sir Isaac Newton to invent the reflecting telescope in 1671.