1) Read: A wave is a disturbance that moves through a medium or through space. This disturbance maybe a displacement of atoms away from their equilibrium positions in an elastic medium, a pulse in a spring, a change in pressure of a gas, or a variation in EM field. There is a transfer of energy in the direction of propagation of the disturbance for each type of wave. 

2) Feel the blanks. Use the word bank.
bank: medium, vibrations, wavelength, air, energy, 3E8 m/s, transverse waves, surface waves, longitudinal waves, water, Lf : L is the wavelength (m) and f is the frequency (Hz or number of cycles per second)

A) Waves transfer ______ without transferring matter.

B) Mechanical waves require a ______. water waves require ____, sound waves requires _____ . EM waves requires no ____________. They travel in a vacuum at a speed of _____

C) In_______   ________ , the displacement of the medium is perpendicular to the direction of wave motion. Example; waves on a rope.

D) In ________   ___________, the displacement is parallel to the wave direction. Example: sound waves.

E) In _____     ___________ matter is displaced in both direction. Example: water waves and Love waves (produced by an earthquake, most damaging).

F) The wave source determines the frequency of a wave f, which is the number of __________________ per second.

G) The medium determines the wave speed which ca be calculated for continuous wave using equation V = _________.

try without hints if you are a Science major.

3) The Sears Building in Chicago sways back and forth in the wind with a frequency of about 0.10 Hz. What is its period of vibration?
(hint: frequency f = number of cycles per second and period T = number of seconds per cycle. so f = 1/T)

4) An ocean wave has a length of 10.0m. A wave passes a fixed location every 2.0s . What is the speed of the wave ?
(hint: V = L f. or V = L/T. You are given seconds per cycle that is T)

5) Water waves in a shallow dish are 6.cm long. At one point, the water oscillates up and down at a rate of 4.8 oscillations per second.
A) What is the speed of the water waves?
B) what is the period of the water waves ?
(hint: you are given the wavelength and the frequency)

6) Water waves in a lake travel 4.4 m in 1.8s. The period of oscillation is 1.2s.
A) what is the speed of the water waves ?
B) What is their wavelength ?
(hint: first find the speed, then L using T)

7) The frequency of yellow light is 5.0 E14Hz. Find the wavelength of yellow light. The speed of light is 300,000 km/s


8) AM radio signals are broadcast at frequencies between 550KZ and 1600KHZ. (kilohertz) and travel 3E8m/s.
A) What is the range of wavelengths for these signals
hint: f1 = 550kHz = 550 000 HZ and v = L1 f1, solve for L1 . same thing for f2.
B) FM frequencies range between 88MHz (megahertz = E6 HZ) and travel at the same speed. What is the range of FM wavelengths?

9) A sonar signal of frequency E6HZ has a wavelength of 1.5 mm in water.
A) What is the speed of the signal in water ?
hint: In water the signal has a lower speed. You need to use V = L f
B) What is its period in water ?
C) What is its period in air ?
hint: The frequency does not depend on the medium. Only the wavelength changes and the speed.

10) A sound wave of wavelength 0.70m and velocity 330m/s is produces for 0.5s.
A) what is the frequency of the wave ?
B) How many complete waves are emitted in this time interval ?
hint: use frequency = number of cycles per second
C) after 0.5 s, how far is the front of the wave from the source of the sound ?

11) extra credits/advanced
The speed of sound in water is 1498m.m/s. A sonar signal is sent straight down from a ship at a point just below the water surface, and 1.8s later the reflected signal is detected. How deep is the ocean beneath the ship ?

12) advanced/extra
The time needed for a water wave to change from the equilibrium level to the crest is 0.18s.
A) What fraction of a wavelength is this ?
B) What is the period of the wave ?
C) What is the frequency of the wave ?

13) advanced/extra
Julius and Caesar are resting on an offshore raft after a swim. THey estimate that 3.0m separates a trough and an adjacent crest of surface waves on the lake. THey count 14 crests that pass by the raft in 20s. Calculate how fast the waves are moving.
(hint: you should find about 872km)

14) advanced/extra
The velocity of a wave on a string depends on how hard the string is stretched, and on the mass per unit length of the string. If Ft is the tension in the string, and u is the mass/unit length, then the velocity, V, can be determined.

V = sqrt(Ft/u)  (sqrt is for square root)

A piece of string 5.30m long has a mass of 15g. WHat must the tension in the string be to make the wavelength of a 125Hz wave 12.0cm?
hint : convert g to kg before computing u. Then compute V. Then compute L using f.

15) EAsy
The length of time it takes a point on a medium carrying a wave to go through one cycle is the __________ of the wave. The recirpcal of a wave's period is its ____________ . The hertz is a measure of ____________. 2 points on a wave that are a half-wavelength apart are _____ degrees out of phase with each ohter. THe maximum displacement of any point on a wave is called the _____________ of the wave at that point. The product of frequency and wavelength gives you the ___________ of a wave.






 

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