Supplemental Instruction
Iowa State University / Leader: / Song
Course: / PHYS 111
Instructor: / Furukawa
Date: / October 25, 2016
Important equations: v = λT = λf；v = Fm；m = mL；I = PA = P4pr2；b = (10dB)log(I/I0)；
I0 = 10-12W/m2；log(A/B) = log(A) – log(B)；log(10±n) = ±n；fbeat = |f1 – f2|.
1. (T/F) Resonance occurs when the frequency of the force matches a natural frequency at which the object will oscillate.
2. (T/F) As a transverse wave on a string moves horizontally, all points on the string vibrate parallel to the direction of wave motion.
3. (T/F) Wavelength is the horizontal length of one cycle of the wave.
4. Microwaves travel with the speed of light, c = 3 x 108 m/s. At a frequency of 10 GHz, these waves cause the water molecules in your burrito to vibrate. What is their wavelength?
A) 0.3 mm
B) 3 cm
C) 30 cm
5. You stand a certain distance away from a speaker and you hear a certain intensity of sound. If you double your distance from the speaker, what happens to the sound intensity at your new position?
A) drops to 1/2 its original value
B) drops to 1/4 its original value
C) does not change
6. A wave pulse can be sent down a rope by jerking sharply on the free end. If the tension of the rope is increased, how will that affect the speed of the wave?
A) speed increases
B) speed does not change
C) speed decreases
7. Sound waves travel in air with a speed of 343 m/s. The lowest frequency sound we can hear is 20.0 Hz, and the highest frequency is 20.0 kHz. Find the wavelength of sound for frequency of 400 Hz.
8. A person was talking in a small room and the sound intensity level is 60 dB everywhere within the room. Now, there are eight people talking in similar manner simultaneously in the room, what is the sound intensity level?