Waves

WavesA wave is any disturbance that transmits energy

through matter or space

Imagine that you just came home from a day at the beach, you had fun, but you’re hungry so you put some leftover pizza in the microwave and listen to the radio while you wait. Your phone rings and it’s your best friend calling to find out if you’ve done science HW yet.

Name some waves in the paragraph above. How many different waves were present?

Waves carry energyEnergy can be carried away from its source by a

wave, but the material through which a wave travels does not move with the energy. Ex: wave in a tidal pool

As a wave travels, it uses energy to do work on everything in its path

Energy transferA medium is a substance through which a wave

can travel. It can be a solid, liquid, or gas.

Some waves transfer energy by the vibration of particles in a medium.

Sound waves need a medium. If there are no particles to vibrate, there will be no sound (vacuum). Ex: tuning fork

Types of wavesMechanical waves: waves that need a medium.

Ex: seismic waves of earthquakes

Electromagnetic waves: waves that do not need a medium and can travel through substances. They travel the fastest through empty space. Ex: visible light

Types of wavesTransverse wave (“moving across”): particles vibrate

in an up and down motion at right angles to the direction the wave travels. Ex: waves on a rope

Longitudinal wave: particles of the medium vibrate back and forth in the direction the wave travels. Ex: a spring. Ex: sound waves from hitting a drum

Compression = when particles are crowded together

Rarefaction = when particles are less crowded than normal

Types of wavesSurface wave: combination of transverse and

longitudinal waves at the boundary between two media

Wave speedThe speed at which a wave travels

Depends on the medium

Can be calculated using wavelength and frequency:

v = λ x f

v = speed

λ= wavelength

f = frequency

Wave speed calculationsThe frequency of a wave is 3/s or 3 Hz. The

wavelength is 0.5 m. What is the wave speed?

The frequency of a wave is 2/s or 2 Hz. The wavelength is 1.5 m. What is the wave speed?

Wave calculationsThe speed of a wave is 20 m/s and it has a

frequency of 4 Hz. What is the wavelength?

The speed of a wave is 15 m/s and it has a frequency of 2 Hz. What is the wavelength?

Wave calculationsA wave has a speed of 20 m/s and a wavelength

of 2.5 m. What is the frequency?

A wave has a speed of 10 m/s and a wavelength of 2 m. What is the frequency?