A-level Physics/Wave properties/Waves

Electromagnetic Waves

The electromagnetic spectrum is a family of waves that share the following properties:

• They are able to transmit through a vacuum.
• They all travel at the same speed in a vacuum (3×10⁸ ms⁻¹).
• They are all transverse waves consisting of magnetic and electric fields oscillating at right angles to each other.
• They all transfer energy as photons (the higher the frequency of a particular radiation the greater the energy contained in each photon.
• They can all be reflected, refracted, diffracted and create interference patterns.
• Properties of these waves change with their frequency / wavelength so they are divided into seven sub groups which are radio wave, microwaves, infra red waves, visible light, ultraviolet, x rays and gamma rays.

Radio Waves

Radio waves are used mainly in communication over short or long distances. Shorter wavelengths are used for television and FM radio while longer wavelengths are used for AM radio.

Long Wave Wavelength = 1*10⁴m
Medium Wave Wavelength = 1*10²m
Short Wave Wavelength = 1*10⁰m

Microwaves

Some microwaves pass easily through Earths atmosphere and are used for communications with satellites and or mobile phones.

Microwaves are also commonly used for cooking with the aid of a microwave oven.

Typical Values are as follows:
Wavelength (m) = 3*10⁻²
Frequency (Hz) = 1*10¹⁰

Definitions

Transverse Wave
The direction of energy transfer is at 90 degrees to the direction of the vibrating particles.

Longitudinal Wave
The particles vibrate backwards and forwards along the line of the direction of the energy transfer in the wave.

Amplitude
The greatest displacement of the wave.

Period (T)
Is the time taken (in seconds) for one complete cycle of the wave.

Frequency (f)
The number of cycles of the wave per second.

Wavelength (λ)
The shortest distance between 2 particles on the wave with the same phase.

Speed of wave
Distance travelled by the wave in one time period. (λ/T)