Part I : MULTIPLE CHOICE

Note: the test you took may have had the questions AND answers in a different order than shown here. Q1: An experienced spear fisherman sees a small fish swimming in a tidal pool. If the fisherman sees the fish at

approximately a 40o angle (measured from vertical), he knows that he must release his spear at what angle? A) Much more than 40o B) A few degrees more than 40o C) Exactly equal to 40o D) A few degrees less than 40o Answer: ____________

Q2: A nearly frictionless mass-spring oscillator with a period of 4 sec is set into motion at t=0 with an initial

maximum amplitude of 40 cm. After t=100 sec, the maximum amplitude has decreased to 20 cm. At what time will the amplitude have decreased to 5 cm?

A) t = 175 sec B) t = 250 sec C) t = 300 sec D) t = 400 sec Answer: ____________

Q3: Astronomers suspect that a particular star is actually a binary system made up of two stars. Using existing

visible light telescopes, however, the two separate stars cannot be resolved. Assuming that diffraction is the primary problem, which of the following techniques might help to improve the resolution?

A) Image the star using a larger frequency such as ultraviolet light B) Image the star using a smaller frequency such as infrared light C) Image the star at the same frequency but using a smaller telescope aperture D) Image the star using radio waves

Answer: ____________ Q4: A slide projector uses a converging lens with a focal length of 6.0 cm. If the images are to be projected onto a

screen 3.7 m away, how far should the slides be placed from the lens? A) 5.9 cm B) 6.0 cm C) 6.1 cm D) 9.6 cm Answer: ____________

Q5: When an auditorium has a solid wall, sound waves will tend to perfectly reflect off the wall (with a 180 o phase change). If listening to music, as from an orchestra, the incoming and reflected waves will interfere with each other. For a listener sitting 0.5m from the wall, what is the lowest frequency which gets suppressed by this interference?

A) 82 Hz B) 165 Hz C) 330 Hz. D) 660 Hz Answer: ____________

Q6: A microwave oven works by producing standing waves of electromagnetic radiation inside a closed housing. Consider a microwave oven which is 30 cm wide and which has five standing wave nodes one at each end of the microwave plus three inside the oven itself. What does the frequency of the radiation need to be to produce this pattern?

A) 0.7 x 109 Hz B) 1.0 x 109 Hz C) 1.5 x 109 Hz D) 2.0 x 109 Hz E) 4.0 x 109 Hz Answer: ____________

Extra Credit (+2 points): Why are real microwave ovens designed with 4 nodes instead of 3 or 5?

4 nodes puts an anti-node in the center, which is where most food goes. At the nodes there is zero amplitude no cooking!

D

C

A

C

B

D