11) A double convex thin glass lens has equal radii of curvature. The focal length of the lens is +37.3 cm and the index of refraction of the glass is 1.52. The radius of curvature of each convex surface, in cm, is closest to:

A) 39

B) 35

C) 31

D) 43

E) 46

12) A double convex thin glass lens has equal radii of curvature. The focal length of the lens is +31.2 cm and the index of refraction of the glass is 1.52. The lens is replaced with a plano-convex glass lens of the same focal length and thickness. The radius of curvature of the convex surface is 13.0 cm. The index of refraction of the glass of the plano-convex lens is closest to:

A) 1.42

B) 1.44

C) 1.40

D) 1.38

E) 1.36

Situation 24.1

An erect object is 50 cm from a concave mirror of radius 60 cm.

13) In Situation 24.1, the character of the image is:

A) real and erect

B) real and inverted

C) virtual and erect

D) virtual and inverted

E) indeterminate

14) In Situation 24.1, the distance of the image from the mirror, in cm, is closest to:

A) 19

B) 35

C) 60

D) 75

E) 120

15) In Situation 24.1, the lateral magnification of the image is closest to:

A) +0.4

B) +0.7

C) +1.5

D) -0.7

E) -1.5

16) In Situation 24.1, the object is moved to a new position, such that the new lateral magnification is +2.5. The new object distance, in cm, is closest to:

A) 18

B) 24

C) 30

D) 36

E) 42

17) Suppose you wanted to start a fire using sunlight and a mirror. Which of the following statements is most accurate?

A) It would be best to use a plane mirror.

B) It would be best to use a convex mirror.

C) It would be best to use a concave mirror, with the object to be ignited positioned at the center of curvature of the mirror.

D) It would be best to use a concave mirror, with the object to be ignited positioned halfway between the mirror and its center of curvature.

E) One cannot start a fire using a mirror, since mirrors form only virtual images.

18) An amateur astronomer grinds a double convex lens whose surfaces have radii of curvature of 40 cm and 60 cm. The glass has an index of refraction of 1.54. What is the focal length of this lens in air?

A) 42.5 cm

B) 126 cm

C) 88.8 cm

D) 44.4 cm

E) 222 cm

19) An object is placed 15.0 cm to the left of a double-convex lens of focal length 20.0 cm. The image of this object is located

A) 60.0 cm to the right of the lens.

B) 60.0 cm to the left of the lens.

C) 8.57 cm to the right of the lens.

D) 8.57 cm to the left of the lens.

E) 30.0 cm to the left of the lens.

20) If a single lens forms a virtual image of an object, then

A) The lens must be a diverging lens.

B) The lens must be a converging lens.

C) The lens could be either a diverging or a converging lens.

D) The image must be inverted.