EM (Electromagnetic) Spectrum

1. radiowaves: phones, TV, WIFI

2. microwaves: cooking (absorbed by water)

3. infra-red: cooking (absorbed by surface)

4. visible light: vision

5. ultra violet: tanning, can cause skin cancer

6. x-rays: medical scans, also dangerous

7. gamma rays: sterilising, medical treatments, also dangerous

All EM waves are emitted and absorbed by electrons (apart from gamma - they’re emitted by NUCLEI).

If the energy of the wave is high enough, it can cause an electron to leave its atom, leaving an ion.

UV, X-rays and gamma are ionising radiation.

Practical:

1. Show that matte black is the best emitter and absorber of IR

2. Use Leslie cube with IR thermometer or tubes wrapped in different materials under source e.g. IR lamp.

3. Shiny materials are the worst emitters and absorbers

shorter wavelength = higher frequency = more energy