Photons and Energy A photon is a bundle of energy. This energy is a type of electromagnetic, or EM wave. The EM spectrum shows how the energies are related to the type of wave produced.

The Electromagnetic Spectrum

As you can see, visible light is only a very small fraction of the types of EM waves that are produced by the sun.

Range of EM waves emitted by the sun

As you can tell, the sun emits all types of radiation, but most of it is in the visible spectrum range (light). Thankfully our atmosphere absorbs most of the damaging x-rays and gamma rays from the sun. Ozone absorbs more than 90% of the UV radiation as well

These are all EM waves and all travel at the same speed, 300,000 km/s (=speed of light) They are a form of light we cannot see. That’s why astronomers have radio, UV, microwave and infrared telescopes. They also have gamma and x-ray telescopes but the atmosphere blocks out most of those rays.

Energy Is Transferred 3 Ways Conduction Convection Radiation

1. Conduction Conduction - the transfer of energy by direct contact. - objects toughing other things - molecular motion ex: touching a hot pot, hot water touching your skin.

2. Convection Convection - the transfer of energy by moving masses of material - the hot water in a pot moving around - warm air coming out of the ducts - a warm breeze that blows across the ground

3. Radiation Radiation – The transfer of energy by waves. The waves are called Electromagnetic waves = (EM) These waves don’t need a material to travel through (a medium)

Radiation isn’t always harmful Normal everyday radiation includes thermal (heat), solar radiation (light from the sun), radio waves, microwaves, etc