## Monday, December 20, 2010

### Displacement- Time graph and displacement -Distance Graph for a wave

The sinusoidal graph shown is a graph of displacement, s against time , t of a load on a spring.

O is called the equilibrium position.

From a displacement-time graph for a wave, we can obtain
i) amplitude, a ,and
ii) period, T.

From a displacement- distance graph for a wave, we can obtain
i) amplitude, a ,and
ii) wavelength, λ

Relationship between Speed, (v) Wavelength,(λ) and Frequency (f)

The speed of a wave is determined by its wavelength, λ, and its frequency, f , according ti the equation V= f λ

For a wave moving at constant speed, increasing the frequency will result in a decrease in the wavelength.

For a wave moving at constant speed, decreasing the frequency will result in an increase in the wavelength.

Work example:

What is the frequency of water waves with the wavelength of 3.0 cm and traveling at a speed of 1.5 cm/s ?

solution :

Step 1: write formula first
V= f λ

step 2 : Substitute all given info into formula
1.5
cm/s = f x 3.0 cm

Step 3:find unknown
f = 0.5 Hz

Wasim said...

Forgive me for asking, but isn't Hz measured in m/s and not in cm/s?

Thanks.

Fizik said...

unit of frequency, f is Hz or 1/s.
m/s or cm/s is the unit of velocity or speed.