Ch. 25

Question 1

A sign painted on a store window is reversed when viewed from inside the store. If a person inside the store views the reversed sign in a plane mirror, does the sign appear as it would when viewed from outside the store?

Answer 1

Yes

Question 2

If a clock is held in front of a mirror, its image is reversed left to right. From the point of view of a person looking into the mirror, does the image of the second hand rotate in the reverse direction?

Answer 2

Yes

Question 3

The photograph shows an experimental device at Sandia National Laboratories in New Mexico. This device is a mirror that focuses sunlight to heat sodium to a boil, which the heats helium gas in an engine. The engine does the work of driving a generator to produce electricity. The sodium unit and the engine are labeled in the photo.

A) what kind of mirror is being used?
B) where is the sodium unit located relative to the mirror?

Answer 3

A) concave

B) located at the focal point of the mirror

Question 4

Is it possible to use a convex mirror to produce an image that is larger than the object?

Answer 4

No

Question 5

Assume that the distance between you and the spoon is greater than the focal length of the spoon.

A) When you look at the back side of a shiny teaspoon at arms length, do you see yourself upright or upside down?

B) When you look at the other side of the spoon, do you see yourself upright or upside down?

Answer 5

A) upright

B) upside down

Question 6

Can the image formed by a concave mirror ever be projected directly into a screen without the help of other mirrors or lenses?

If so, specify where the object should be placed relative to the mirror.

Answer 6

Yes, provided the object distance is greater than the focal length of the mirror

Question 7

Can the image formed by a convex mirror ever be projected directly into a screen without the help of other mirrors or lenses?

If so, specify where the object should be placed relative to the mirror.

Answer 7

It is not possible for a convex mirror to project an image directly onto a screen.

Question 8

Suppose that you stand in front of a spherical mirror (concave or convex).

Is it possible for your image to be real and upright?

Answer 8

No

Question 9

Suppose that you stand in front of a spherical mirror (concave or convex).

Is it possible for your image to be virtual and inverted?

Answer 9

No

Question 10

An object is placed between the focal point and the center of curvature of a concave mirror. The object is then moved closer to the mirror, but still remains between the focal point and the center of curvature.

A) Does the magnitude of the image distance become larger or smaller?

B) Does the magnitude of the image height become larger or smaller?

Answer 10

A) Larger

B) Larger

Question 11

When you see the image of yourself formed by a mirror, it is because 1) light rays actually coming from a real image enter your eyes or 2) light rays appearing to come from a virtual image enter your eyes.

If light rays from the image do not enter your eyes, you do not see yourself.

Are there any places on the principal axis where you cannot see yourself when you are standing in front of a mirror that is A) convex B) concave? If so, where are these places? Assume that you only have the one mirror to use.

Answer 11

A) No, you can see yourself anywhere on the principal axis

B) You cannot see yourself when you are between the center of curvature and the focal point of the mirror because your image is behind you.

Question 12

An object is placed in front of a spherical mirror, and the magnification or the system is m=-6. What does this number tell you about the image?

Answer 12

• The image is larger than the object.
• The image is inverted relative to the object.
• The image is a real image.

Question 13

Plane mirrors and convex mirrors form virtual images. With a plane mirror, the image may be infinitely far behind the mirror, depending on where the object is located in front of the mirror. For an object in front of a single convex mirror, what is the greatest distance behind the mirror at which the image can be found?

Answer 13

The image will never be located beyond the focal point

Question 14

A ray is ___.

Answer 14

Parallel to the velocity of the wave.

Question 15

Rays of light coming from the sun (a very distant object) are near and parallel to the principal axis of a concave mirror. After reflecting from the mirror, where will the rays cross each other at a single point? The rays ___.

Answer 15

Will cross at the focal point

Question 16

Which one of the following statements concerning spherical mirrors is correct?

Answer 16

Only a concave mirror can produce an enlarged image, provided the object distance is less than the radius of curvature.

Question 17

Suppose that you hold up a small convex mirror in front of your face. Which answer describes the image of your face?

Answer 17

Virtual, upright

Question 18

An object is placed at a known distance in front of a mirror whose focal length is also known. You apply the mirror equation and find that the image distance is a negative number. This result tells you that….

Answer 18

The image is virtual

Question 19

An object is situated at a known distance in front of a convex mirror whose focal length is also known. A friend of yours does a calculation that shows that the magnification is -2.

After some thought, you conclude correctly that…

Answer 19

The magnification should be +1/2

Question 20

Wave fronts -

Answer 20

Surfaces on which all points of a wave are in the same phase of motion

Question 21

Plane waves -

Answer 21

Waves whose wave fronts are flat surfaces

Question 22

Rays -

Answer 22

Lines that are perpendicular to the wave fronts and point in the direction of the velocity of the wave

Question 23

Law of reflection -

Answer 23

The incident ray, the reflected ray, and the normal to the surface all lie in the same plane, and the angle of reflection theta(r), equals the angle of incidence theta(i)

Question 24

Virtual image -

Answer 24

All the rays of light do not actually come, but only appear to do so

Question 25

Real image -

Answer 25

All the rays of light actually do emanate

Question 26

Image a plane mirror forms?

Answer 26

Upright, virtual image that is located as far behind the mirror as the object is in front of it

The heights of the image and the object are equal

Question 27

Convex mirror -

Answer 27

Outside surface is polished

Question 28

Concave mirror -

Answer 28

Inside surface is polished

Question 29

Principal axis of a mirror -

Answer 29

Straight line drawn through the center of curvature and the middle of the mirrors surface

Question 30

Paraxial rays -

Answer 30

Rays that are close to the principal axis

Question 31

Radius of curvature R -

Answer 31

The distance from the center of curvature to the mirror

Question 32

Focal point of a concave spherical mirror -

Answer 32

A point on the principal axis, in front of the mirror

Question 33

Focal point of a convex spherical mirror -

Answer 33

A point on the principal axis, behind the mirror

Question 34

Spherical aberration -

Answer 34

The fact that a spherical mirror does not bring all rays parallel to the principal of axis to a single image point after reflection

Question 35

Focal length -

Answer 35

The distance along the principal axis between the focal point and the mirror

Question 36

The image produced by a mirror can be located by a graphical method known as ___.

Answer 36

Ray tracing

Question 37

For a concave mirror, the following paraxial rays are useful for ray tracing..

Answer 37

• this ray leaves the object traveling parallel to the principal axis. The ray reflects from the mirror and passes through the focal point
• this ray leaves the object and passes through the focal point. The ray reflects from the mirror and travels parallel to the principal axis
• this ray leaves the object and travels along a line that passes through the center of curvature. The ray strikes the mirror perpendicularly and reflects back on itself

Question 38

For a convex mirror, the following paraxial rays are useful for ray tracing..

Answer 38

• this ray leaves the object traveling parallel to the principal axis. After reflection from the mirror, the ray appears to originate from the focal point of the mirror
• this ray leaves the object and heads toward the focal point. After reflection, the ray travels parallel to the principal axis
• this ray leaves the object and travels toward the center of curvature. The ray strikes the mirror perpendicularly and reflects back on itself