Waves (no math)
List the 5 principle characteristics of a wave:
-amplitude
-wave speed
-wavelength
-period
-frequency
Find the frequency of a tuning fork that takes 2.5 ✕ 10^-3 s to complete one oscillation
400 Hz
What is the sonic range of a human?
20-20k Hz
The length of a certain pendulum is 9.8m. What is its period?
6.28 seconds
True or false: All waves need a medium to travel through.
False
An ultrasound wave is used to measure the depth of a lake. The speed of sound in water is 1480 m/s, and the wave takes 0.12 seconds to travel to the lake bottom and back. How deep is the lake?
88.8m
If you are traveling towards a stationary sound source, you will hear the sound at a (higher OR lower) ________(wave characteristic).
(your answer should be 2 words
higher frequency
TRUE or FALSE (you must get both problems correct to get the points)
1) A sound wave is an example of a transverse wave
2) When waves reflect off a surface, the reflected wave has the same frequency as the incident wave
1) False
2) True
Waves can interfere constructively or __________. When they interfere constructively, their ________ increases.
destructively; amplitude
A boat in the trough of a wave takes 3 seconds to reach the highest point of the wave. The velocity of the wave is 5 m/s. What is its wavelength?
30m
What are the 3 main ways humans perceive sound?
Pitch
Quality (or Timbre)
Loudness
The fundamental frequency of a string is 4Hz. What is the period of the 8th harmonic
0.03125 s
(1/32Hz)
Name 2 factors that effect the period of a pendulum
1) Pendulum length
2) (acceleration due to) Gravity
The fifth harmonic of a wave has a frequency of 65Hz. What is the fundamental frequency of the wave?
13 Hz
You are moving away from a sound source, which is also moving away from you (ie. you are fleeing from each other). Write the doppler effect equation (with correct + and/or -) that you would use to solve this.
fo=fs((v-vo)/(v+vs))
Rank the following in terms of how fast sound will travel through them, generally speaking (fastest to slowest):
-Cool air
-Liquid
-Solid
-Warm air
Solid > Liquid > Warm air > Cool air
What are the 3 things that can happen when a wave reaches a boundary?
-reflection
-transmission
-absorbtion
A 72cm long string vibrates so that it forms a standing wave with two antinodes.
a) which harmonic does this wave represent?
b) determine the wavelength of the wave?
c) how many nodes are there is this wave pattern?
a) 2nd
b) 0.72m
c) 3 nodes
While standing 8m from a spherical speaker, you hear the music at half the intensity of the threshold of pain. What is the wattage of the speaker?
402 Watts
(threshold of pain is 1 W/m2; threshold of hearing is 1*10-12 W/m2)
You are running after a pickpocket at 4 m/s while screaming at a pitch of 700Hz to attract attention. The pickpocket sprints away at 6 m/s. What pitch does the thief hear you screaming at?
The speed of sound on this day is 340m/s.
696 Hz
fo=fs((v-vo)/(v-vs))