1. 7.12 Electromagnetic Waves(2)
Rays and Waves
7.12 Electromagnetic Waves(2)

2. ELECTROMAGNETIC SPECTRUM
Transverse waves created by the sun as well as electrical and magnetic energy sources and sent through the vacuum of space to Earth. The complete electromagnetic spectrum is given below:
Radio waves (including TV signals)
Microwaves
Infrared radiation
Visible Light
X-rays
Gamma rays

4. Radio Waves
This is the same kind of energy that radio stations emit into the air . But radio waves are also emitted by other things ... such as stars and gases in space.
VHF and UHF waves have shorter wavelengths. VHF is used for stereos and UHF for TV broadcast.

5. Long and medium waves will diffract around hills, so a radio can still receive signals even if a hill blocks the direct route from source.

6. Microwaves
Microwaves have wavelengths that can be measured in centimetres!
Microwaves are good for transmitting information from one place to another.
Shorter microwaves are
used in remote sensing.

7. Infrared Radiation
Infrared light lies between the visible and microwave portions of the electromagnetic spectrum. "Near infrared" light is closest in wavelength to visible light and "far infrared" is closer to the microwave region of the electromagnetic spectrum.
Infrared can produce heat.

8. Ultraviolet Radiation
Ultraviolet (UV) light has shorter wavelengths than visible light.
The Sun’s UV ray is harmful to living cells, it can cause skin cancer.
UV rays are used in some types of sterilising equipments to kill bacteria.

9. X-Rays
X-Rays are given off when fast moving electrons lose energy very quickly. X-rays can penetrate bones.

10. Gamma Rays
Gamma-rays are generated by radioactive atoms and in nuclear explosions.
Gamma-rays can kill living cells, a fact which medicine uses to its advantage, using gamma-rays to kill cancerous cells.