Transcript Rays and Waves - Explore Physics

Rays and Waves
7.12 Electromagnetic Waves(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
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.
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.
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.
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.
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.
X-Rays
 X-Rays are given off when fast moving
electrons lose energy very quickly. X-rays
can penetrate bones.
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 gammarays to kill cancerous cells.