U4AOS1 Topic 14: Electromagnetic Waves

Electromagnetic waves are waves which have a magnetic component to the wave which propagates perpendicular to the electrical wave which are produced by the acceleration of charged particles.

All electromagnetic waves travel at the speed of light regardless of the frequency.

$c = f\lambda=\frac{\lambda}{T}$

Examples of electromagnetic waves from highest wavelength to lowest.

Radio waves: Travel long distances and have extremely low energy due to the long wavelengths.

Microwaves: The resonant frequency of water; which causes water molecules to vibrate allowing us to cook food in a microwave.

Infrared: Living organisms emit infrared light as heat. TV remotes also use infrared light to send signals but still have low energy.

Visible light: Normal light that we can see. It still has low energy but increasing in energy due to shorter wavelength. Red has the lowest energy and purple-blue has the highest.

Ultraviolet (UV) light: Sterilises environments due to its energy levels which kills bacteria. Also causes skin cancer in people when subjected to large amounts over a long period.

X-ray: High energy. Can pass through all parts of the body except for bones. High concentrations damage DNA and can cause cancer.

Gamma rays: High energy. Kill cells instantly. Only produced naturally by objects in space colliding or exploding.

Photons have an energy depending on the frequency they travel at. The energy of a single photon is calculated through the formula

$E = hf$

$6.62\times 10^{-34} Js$

Since light is made up of photons the intensity of the light aka how bright or dim is the light is depends on how many photons are in that area. A very bright light will have a lot of photons whereas a very dim light will have a small amount of photons.