X-rays and gamma rays are types of electromagnetic radiation used in medicine and to kill bacteria. They can damage living tissue in large doses by killing cells, and cause cancer in small doses. Gamma rays have the shortest wavelengths and are used to sterilize equipment and kill cancer cells. Microwaves are used for communication and in cooking by heating water molecules. Infrared rays are emitted by all hot objects and are used in devices like heaters, night vision cameras, and remote controls.

1. X-rays are used X-rays and gamma Gamma rays Microwaves Infrared-IR
in hospitals to rays damage living •Have the shortest •Short waves •All objects emit IR. The hotter
take radiographs. tissue when they wavelengths •Can pass through the object the more IR it emits
pass through it. • used to kill atmosphere for satellite •IR heat objects.
bacteria in food, communications •Uses: heaters, IR scanners, IR
Large doses can kill
sterilise surgical •Used in cooking, microwave cameras, remote controls, optical
cells, small doses
equipment and kill ovens - heat water molecules fibres and communications
can cause cancer
cancer cells.
X-rays and gamma rays are absorbed
by dense material such as bone and
metal but pass through soft tissue
Radio waves
Optical Fibres
•Have the longest wavelengths
•Visible light and IR carry
•Used in communications
signals
•Radio waves - smallest long waves -
•Carry more info than wires
300,000Hz+
•More secure, signal stays in
•Carry radio, TV, mobile phone signals
wire
•Alternating voltage  ariel  receiver
•Frequency of radio wave = alternating
voltage of carrier wave
•High frequency radio waves-
•Carry more information Analogue signals vary
•Have a shorter range continuously in amplitude or
•Less diffraction frequency
Digital signals are on or off.
Radio waves are Digital signal free of
reflected by the interference and carry more
IONOSPHERE. information.
P1b, Physics
Carrier waves (radio,
Stronger in microwaves etc) carries
summer digital/analogue signal
Ultraviolet-UV
Found naturally in sunlight.
UV harms the skin and The use of
eyes, causes a sun tan, used radio waves
All EM waves travel through space at speed of in security markers depends on
light (300 million m/s).
the frequency
Wave speed= Frequency X Wavelength of the waves
(m/s) (Hz) (m)

2. Alpha particle
A radioactive substance
Marie Curie- Positive charge, deflected in magnetic and
contains unstable nuclei.
Discovered electric fields, Helium nucleus
An unstable nucleus
Radioactivity. Beta particle
becomes stable by
Worked with Negative charge, deflected in magnetic
emitting radiation.
uranium. Died of and electric fields, electron emitted from
cancer because nucleus
of her work. Alpha Radiation- Stopped by paper or a Gamma particles
few cm of air No charge, not deflected in magnetic and
Beta Radiation– Stopped by thin aluminium electric fields, EM wave
or about 1m of air
Gamma radiation- Stopped by thick lead or
concrete and has an unlimited range in air Uses of radioactivity
•Automatic thickness monitoring- uses beta
Half life •Radioactive tracers- uses gamma
Unstable radioactive elements decay Time it takes for number of •Radioactive carbon/uranium dating
randomly and give off particles radioactive nuclei of the isotope to •Carbon- wood
Isotope atoms of an element have decay to half its initial value. •Uranium- rocks
different numbers of neutrons •Smoke detectors- uses alpha
Detect radiation with Geiger Muller
Tube (GM tube) Big Bang (BB)Theory
•Massive explosion from a
Isotopes small point
Different •Background microwave
types of radiation is radiation
atoms of created just after the BB.
the same •Created as high energy
chemical gamma radiation after BB
element, The Earths atmosphere
Ionisation- Alpha and beta particles As universe expanded, it
each having absorbs all electromagnetic
knock electrons out of atoms stretched into longer and
a different waves, except visible light,
longer wavelengths.
number of radio waves and some UV
neutrons P1b Physics radiation.
Satellite detectors are used
to make observations outside
•Light from distant galaxy is red- the visible and radio spectrum.
shifted to longer wavelengths Clear images are observed
•Edwin Hubble discovered that light using telescopes on satellites
from galaxies were red-shifted detecting visible light.
•Distant galaxies are moving away
from us •Space, time and matter created
•Speed of distant galaxy is by the Big Bang
The most distant galaxies are
proportional to distance from us •BIG BANG happened 13,000
about 13 million light years away.
The universe is expanding million years ago