240 Practice Exam 1
Exam 1 will be 4 questions only
1) An object is placed 6.0 cm in front of a convex mirror with a radius of curvature of 16.0 cm. Which of the
following statements describes the image?
A) The image is inverted and 3.4 cm in front of the mirror.
B) The image is upright and 3.4 cm behind the mirror.
C) The image is upright and 3.4 cm in front of the mirror.
D) The image is inverted and 3.4 cm behind the mirror.
2) John's face is 20 cm in front of a concave shaving mirror. If he observes his image to be twice as big and erect,
what is the focal length of the mirror?
A) 50 cm
B) 30 cm
C) 40 cm
D) 10 cm
E) 20 cm
3) An oil layer that is 5.0 cm thick is spread smoothly and evenly over the surface of water on a windless day.
What is the angle of refraction in the water for a ray of light that has an angle of incidence of 45° as it enters
the oil from the air above? (The index of refraction for oil is 1.15, and for water it is 1.33.)
A) 52°
B) 39°
C) 32°
D) 36°
E) 27°
4) A thin converging lens is found to form an image of a distant building 24 cm from the lens. If an object is
placed 16 cm from the lens, how far from the object will the image be?
A) 48 cm
B) 72 cm
C) 64 cm
D) 32 cm
E) 96 cm
5) A 4.0-cm-tall object is placed 50.0 cm from a diverging lens of focal length 25.0 cm. What is the nature and
location of the image?
A) A virtual image, 2.0 cm tall, 10 cm other side of the object
B) A real image, 1.3 cm tall, 16.7 cm same side as the object
C) A real image, 4.0 cm tall, 20 cm other side of the object
D) A virtual image, 4.0 cm tall, 20 cm other side of the object
E) A virtual image, 1.3 cm tall, 16.7 cm same side as the object
6) A spaceship takes a nonstop journey to a planet and returns in 10 hours according to a clock on the
spaceship. If the speed of the spaceship is 0.80c, how much time has elapsed on the Earth?
A) 7.0 h
B) 17 h
C) 19 h
D) 15 h
E) 3.2 h
7) A meter stick is moving toward you with a speed of 0.85c. What is its length?
A) zero
B) 0.74 m
C) 0.47 m
D) 1.0 m
E) 0.53 m
8) With respect to the earth, object 1 is moving at speed 0.80c to the right. Object 2 is moving in the same
direction at speed 0.80c with respect to object 1. How fast is object 2 moving with respect to the earth?
A) 0.16c
B) 0.98c
C) 1.6c
D) 0.64c
E) 0.80c
9) The atomic bomb that was dropped on Nagasaki in 1945 killed 140,000 people, helping to end World War II
on the next day. It released energy equivalent to that of 20,000 tons of TNT explosive. How much mass was
converted to energy when this took place? (1000 tons of TNT = 4.3 × 10 12 J) Incidentally, modern H-bombs
have energy yields 1000 times as much!
A) 10 kg
B) 1 g
C) 1 kg
D) 10 g
E) 100 g
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Answer Key
Testname: 240PREX1SP15
1) B
2) C
3) C
4) D
5) E
6) B
7) E
8) B
9) B
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