Waves

amplitude
wavelength
frequency
velocity

Longitudinal waves
Transverse waves
Interference

Constructive
Destructive

Doppler Effect

Example questions given in class
1) What is the wavelength of note A (f= 440 Hz) above middle C on the musical scale (speed of sound v = 343 m/s)

frequency = velocity/wavelength
wavelength = velocity / frequency
= (331 m/s) / (440 l/s) = 0.75 m

frequency = velocity/wavelength
wavelength = velocity / frequency
= (331 m/s) / (40,000 l/s) = 0.0083

The following problems have been adapted from Hewitt, Suchocki and Hewitt, Conceptual Physical Science (a text previously used for this course):

Qu 1: You watch a person hammering at a distance and notice that you see the hammer strike a blow one second before you hear the sound. How far away is the person?

Ans. Light travels very fast - almost instantly at this distance
Sounds travels 331 m/s
Since there is one beat defference in a second, woman is 331 meters away.

Qu 2a: A skipper notices wave crests passing the anchor chain every 5 seconds. He estimates the distance between wave crests to be 15 meters. What is the velocity of the waves?

period = 5 seconds; distance between crests = 15 m;
velocity = distance/ time = 15 m / 5s = 3 m/s

Qu 2b: What is the frequency?
Frequency = 1/period = 0.2 Hertz

Qu 3: Radio waves travel at speed of light, = 300,000 km/s = 300,000,000 m/s. What is the wavelength of radio waves that you receive at 106,100,100 (106.1 - NPR) Hertz on your radio dial?

Ans. velocity = wavelength * frequency
Wavelength = velocity / frequency
Wavelength = 300,000,000 m/s / 106,100,000 Hertz = 2.83 meters

Qu 4: A mosquito flaps its wings at 600 vibrations per second (hence the annoying buzz). What is the wavelength of the mosquito's sound?

Ans. 4: wavelength = velocity / freq = 340 m/s / 600 Hertz = 0.6 m

Qu 5: An oceanic deep-sounding vesset surveys the occean bottom with ultrasonic sound that travels 1530 m/s in seawater. How deep is the water if the time delay of the echo from the ocean floor is 6 seconds?

Ans. 5: velocity = distance / time
v = 1530 m/s, t = 6s
distance = v * t =
6seconds * 1530 m/s = 4590 m