Question 1

In a cinema, a picture 2.5 cm wide on the film is projected to an image 3.0 m wide on a screen which is 18 m away. The focal length of the lens is about:

Accepted Answer

A)  7.5 cm 
B)  10 cm 
C)  12.5 cm 
D)  15 cm 
E)  20 cm 
A)  7.5 cm 
B)  10 cm 
C)  12.5 cm 
D)  15 cm 
E)  20 cm

Question 2

A converging lens of focal length 20 cm is placed in contact with, and to the left of, a diverging lens of focal length 30 cm. If an object is placed 40 cm to the left of the converging lens, the total magnification is:

Accepted Answer

A)  -3.0 
B)  -1.5 
C)  -1.0 
D)  2.0 
E)  3.0 
A)  -3.0 
B)  -1.5 
C)  -1.0 
D)  2.0 
E)  3.0

Question 3

If the image distance is negative,

Accepted Answer

A)  the image is real. 
B)  the image is virtual. 
C)  the mirror is concave. 
D)  you have made a mistake; image distances must be positive. 
E)  the object distance must also be negative. 
A)  the image is real. 
B)  the image is virtual. 
C)  the mirror is concave. 
D)  you have made a mistake; image distances must be positive. 
E)  the object distance must also be negative.

Question 4

A converging lens is symmetric; its curved sides have radii of 50 cm. If the focal length is to be 80 cm, what should the index of refraction be?

Accepted Answer

A)  0 
B)  0.3 
C)  0.6 
D)  1.3 
E)  1.6 
A)  0 
B)  0.3 
C)  0.6 
D)  1.3 
E)  1.6

Question 5

A card marked IAHIO8 is standing upright in front of a plane mirror. Which of the following is NOT true?

Accepted Answer

A)  The image is virtual 
B)  The image shifts its position as the observer shifts his position 
C)  The image appears as 8OIHAI to a person looking in the mirror 
D)  The image is caused mostly by specular rather than diffuse reflection 
E)  The image is the same size as the object 
A)  The image is virtual 
B)  The image shifts its position as the observer shifts his position 
C)  The image appears as 8OIHAI to a person looking in the mirror 
D)  The image is caused mostly by specular rather than diffuse reflection 
E)  The image is the same size as the object

Question 6

A convex spherical mirror has a focal length of 12 cm. If an object is placed 6 cm in front of it the image position is:

Accepted Answer

A)  4 cm behind the mirror 
B)  4 cm in front of the mirror 
C)  12 cm behind the mirror 
D)  12 cm in front of the mirror 
E)  at infinity 
A)  4 cm behind the mirror 
B)  4 cm in front of the mirror 
C)  12 cm behind the mirror 
D)  12 cm in front of the mirror 
E)  at infinity

Question 7

An erect object is 2f in front of a convex lens of focal length f. The image is:

Accepted Answer

A)  real, inverted, magnified 
B)  real, erect, same size 
C)  real, inverted, same size 
D)  virtual, inverted, reduced 
E)  real, inverted, reduced 
A)  real, inverted, magnified 
B)  real, erect, same size 
C)  real, inverted, same size 
D)  virtual, inverted, reduced 
E)  real, inverted, reduced

Question 8

At what distance in front of a concave mirror must an object be placed so that the image and object are the same size?

Accepted Answer

A)  one focal length 
B)  half the focal length 
C)  twice the focal length 
D)  less than half the focal length 
E)  more than twice the focal length 
A)  one focal length 
B)  half the focal length 
C)  twice the focal length 
D)  less than half the focal length 
E)  more than twice the focal length

Question 9

Two thin lenses (focal lengths f1 and f2) are in contact. Their equivalent focal length is:

Accepted Answer

A)  f1 + f2 
B)  f1f2/(f1 + f2) 
C)  1/f1 + 1/f2 
D)  f1 - f2 
E)  f1(f1 - f2)/f2 
A)  f1 + f2 
B)  f1f2/(f1 + f2) 
C)  1/f1 + 1/f2 
D)  f1 - f2 
E)  f1(f1 - f2)/f2

Question 10

The focal length of a spherical mirror is N times its radius of curvature where N is:

Accepted Answer

A)  1/4 
B)  1/2 
C)  1 
D)  2 
E)  4 
A)  1/4 
B)  1/2 
C)  1 
D)  2 
E)  4

Question 11

The image produced by a convex mirror of an erect object in front of the mirror is always:

Accepted Answer

A)  virtual, erect, and larger than the object 
B)  virtual, erect, and smaller than the object 
C)  real, erect, and larger than the object 
D)  real, erect, and smaller than the object 
E)  none of the above 
A)  virtual, erect, and larger than the object 
B)  virtual, erect, and smaller than the object 
C)  real, erect, and larger than the object 
D)  real, erect, and smaller than the object 
E)  none of the above

Question 12

The angle between a horizontal ruler and a vertical plane mirror is 30  $\degree$. The angle between the ruler and its image is:

Accepted Answer

A)  15  $\degree$ 
B)  30  $\degree$ 
C)  60  $\degree$ 
D)  90  $\degree$ 
E)  180  $\degree$ 
A)  15  $\degree$ 
B)  30  $\degree$ 
C)  60  $\degree$ 
D)  90  $\degree$ 
E)  180  $\degree$

Question 13

Real images formed by a spherical mirror are always:

Accepted Answer

A)  on the side of the mirror opposite the object 
B)  on the same side of the mirror as the object but closer to the mirror than the object 
C)  on the same side of the mirror as the object but closer to the mirror than the focal point 
D)  on the same side of the mirror as the object but further from the mirror than the focal point 
E)  none of the above 
A)  on the side of the mirror opposite the object 
B)  on the same side of the mirror as the object but closer to the mirror than the object 
C)  on the same side of the mirror as the object but closer to the mirror than the focal point 
D)  on the same side of the mirror as the object but further from the mirror than the focal point 
E)  none of the above

Question 14

Where must an object be placed in front of a converging lens in order to obtain a virtual image?

Accepted Answer

A)  At the focal point 
B)  At twice the distance to the focal point 
C)  Anywhere beyond the focal point 
D)  Between the focal point and the lens 
E)  Between the focal point and twice the distance to the focal point 
A)  At the focal point 
B)  At twice the distance to the focal point 
C)  Anywhere beyond the focal point 
D)  Between the focal point and the lens 
E)  Between the focal point and twice the distance to the focal point

Question 15

The term "virtual" as applied to an image made by a mirror means that the image:

Accepted Answer

A)  is on the mirror surface 
B)  cannot be photographed by a camera 
C)  is in front of the mirror 
D)  is the same size as the object 
E)  cannot be shown directly on a screen 
A)  is on the mirror surface 
B)  cannot be photographed by a camera 
C)  is in front of the mirror 
D)  is the same size as the object 
E)  cannot be shown directly on a screen

Question 16

An object faces a spherical refracting surface. If r is negative,

Accepted Answer

A)  the surface is convex. 
B)  the surface is concave. 
C)  the image must be real. 
D)  the object distance must be negative. 
E)  this cannot happen; r must be positive. 
A)  the surface is convex. 
B)  the surface is concave. 
C)  the image must be real. 
D)  the object distance must be negative. 
E)  this cannot happen; r must be positive.

Question 17

A light bulb burns in front of the center of a 40-cm wide mirror that is hung vertically on a wall. A man walks in front of the mirror along a line that is parallel to the mirror and twice as far from it as the bulb. The greatest distance he can walk and see the image of the bulb at all times is:

Accepted Answer

A)  20 cm 
B)  40 cm 
C)  60 cm 
D)  80 cm 
E)  120 cm 
A)  20 cm 
B)  40 cm 
C)  60 cm 
D)  80 cm 
E)  120 cm

Question 18

Let fo and fe be the focal lengths of the objective and eyepiece of a compound microscope. In ordinary use, the object:

Accepted Answer

A)  is less than fo from the objective lens 
B)  is more that fo from the objective 
C)  produces an intermediate image which is slightly more than fe from the eyepiece 
D)  produces an intermediate image which is 2fe away from the eyepiece 
E)  produces an intermediate image which is less than fo from the objective 
A)  is less than fo from the objective lens 
B)  is more that fo from the objective 
C)  produces an intermediate image which is slightly more than fe from the eyepiece 
D)  produces an intermediate image which is 2fe away from the eyepiece 
E)  produces an intermediate image which is less than fo from the objective

Question 19

A convex refracting surface has a radius of 12 cm. Light is incident in air (n = 1) and refracted into a medium with an index of refraction of 2. To obtain light with rays parallel to the central axis after refraction a point source should be placed on the axis:

Accepted Answer

A)  3 cm from the surface 
B)  6 cm from the surface 
C)  12 cm from the surface 
D)  18 cm from the surface 
E)  24 cm from the surface 
A)  3 cm from the surface 
B)  6 cm from the surface 
C)  12 cm from the surface 
D)  18 cm from the surface 
E)  24 cm from the surface

Question 20

The objective lens of the Yerkes telescope (the largest functioning refracting telescope in the world) has a focal length of 19.4 m. If its eyepiece has a focal length of 2.5 cm, what is the magnitude of its magnification?

Accepted Answer

A)  7.8 
B)  13 
C)  130 
D)  780 
E)  cannot be calculated without knowing the length of the telescope 
A)  7.8 
B)  13 
C)  130 
D)  780 
E)  cannot be calculated without knowing the length of the telescope

Exam 34: Images

In a cinema, a picture 2.5 cm wide on the film is projected to an image 3.0 m wide on a screen which is 18 m away. The focal length of the lens is about:

A converging lens of focal length 20 cm is placed in contact with, and to the left of, a diverging lens of focal length 30 cm. If an object is placed 40 cm to the left of the converging lens, the total magnification is:

If the image distance is negative,

A converging lens is symmetric; its curved sides have radii of 50 cm. If the focal length is to be 80 cm, what should the index of refraction be?

A card marked IAHIO8 is standing upright in front of a plane mirror. Which of the following is NOT true?

A convex spherical mirror has a focal length of 12 cm. If an object is placed 6 cm in front of it the image position is:

An erect object is 2f in front of a convex lens of focal length f. The image is:

At what distance in front of a concave mirror must an object be placed so that the image and object are the same size?

Two thin lenses (focal lengths f1 and f2) are in contact. Their equivalent focal length is:

The focal length of a spherical mirror is N times its radius of curvature where N is:

The image produced by a convex mirror of an erect object in front of the mirror is always:

The angle between a horizontal ruler and a vertical plane mirror is 30 °\degree° . The angle between the ruler and its image is:

Real images formed by a spherical mirror are always:

Where must an object be placed in front of a converging lens in order to obtain a virtual image?

The term "virtual" as applied to an image made by a mirror means that the image:

An object faces a spherical refracting surface. If r is negative,

A light bulb burns in front of the center of a 40-cm wide mirror that is hung vertically on a wall. A man walks in front of the mirror along a line that is parallel to the mirror and twice as far from it as the bulb. The greatest distance he can walk and see the image of the bulb at all times is:

Let fo and fe be the focal lengths of the objective and eyepiece of a compound microscope. In ordinary use, the object:

A convex refracting surface has a radius of 12 cm. Light is incident in air (n = 1) and refracted into a medium with an index of refraction of 2. To obtain light with rays parallel to the central axis after refraction a point source should be placed on the axis:

The objective lens of the Yerkes telescope (the largest functioning refracting telescope in the world) has a focal length of 19.4 m. If its eyepiece has a focal length of 2.5 cm, what is the magnitude of its magnification?

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Two thin lenses (focal lengths f₁ and f₂) are in contact. Their equivalent focal length is:

The angle between a horizontal ruler and a vertical plane mirror is 30 $\degree$ . The angle between the ruler and its image is:

Let f_o and f_e be the focal lengths of the objective and eyepiece of a compound microscope. In ordinary use, the object: