Characteristics of waves

Pg. 47

Daily Sciencepg. 48 Name the two main types of waves. What are the two sub categories of waves? Draw the two types of waves and label the

parts in each. What is the equation for speed? What is the unit for speed?

Wave Properties

Amplitude: The maximum distance that the particles of a wave are displaced from their normal resting positions.

In transverse waves, the amplitude is the distance from the resting position to either the crest or trough.

All transverse waves have a similar shape called a sine curve. Waves that have sine curves are called sine waves.

Wave Properties Wavelength: the distance from any point on a wave to

an identical point on the next wave. In a transverse wave, it is the distance from crest to crest

or trough to trough. In a longitudinal wave, it is the distance between two

compressions or two rarefactions. It is represented by the Greek letter lambda ( ) Wave length is measured in meters.

Amplitude and Wavelength

They are both measurements of distance. They tell us about the energy of a wave.

The larger the amplitude, the more energy it carries The shorter the wavelength, the more energy it carries

Wave Properties

Period: The time it takes to complete one cycle or wave oscillation to occur.

The period is the time it takes for one wavelength to pass by.

In equations, it is represented by the letter, T. It is measured in seconds.

Wave Properties

Frequency: the number

of wavelengths that pass

a point in a given time interval.

The symbol for frequency is, f.

The unit for frequency is the Hertz (Hz).

You can hear from 20 Hz to 20,000 Hz.

Relation btw. f and T

Frequency= 1/ period Example: if a wave in the ocean passes

every 2 seconds, what is the frequency?

Wave Speed

Wave speed: is equal to wavelength divided by the period.

Wave speed = / T

Because the period is the inverse of time, wave speed can also equal the frequency times the wavelength.

Wave speed = x f

Examples

The average wavelength in a series of ocean waves is 15 m. A wave crest arrives at the shore every 10 seconds, so the frequency is 0.1 Hz. What is the average speed of the waves.

Green light has a wavelength of 5.20 x 10-7 m. The speed of light is 3.00 x 10 8 m/s. Calculate the frequency of green light waves with this wavelength.

Speed

The speed depends on the medium Sound waves travel faster in solids than they

do in air. Waves travel differently in liquids, solids and

gasses because of the arrangement of the particles.

Speed of light

Light travels at 3.0 x 108 m/s. This is called the speed of light. It is represented by the letter c. We can see light with frequencies ranging

from 4.3 x 1014 Hz to 7.5 x 1014 Hz. This is called visible light.

All light is contained on the electromagnetic spectrum.

The Doppler effect

Doppler effect: an observed change in the frequency of a wave when the source or the observer is moving.

Frequency determines the pitch, or how high or low something sounds.