GCSE PHYSICS - What is Electromagnetic Radiation? - Wave - Photon - Speed - Frequency - Wavelength - Spectrum (original) (raw)

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What is Electromagnetic Radiation?

Allelectromagnetic radiationtravels at the same speed (in avacuum).
Electromagnetic radiation travels very quickly.
There is nothing which can travelfaster.
The speed is 300,000,000 m/s in avacuum
(that is 300 million metres persecond - not easy to imagine!).

Electromagnetic radiation can be thought of as particles or waves
(the word radiation is also used for radioactivity).

Electromagnetic radiation has a wide variety of wavelengths and frequencies which form the electromagnetic spectrum.

Electromagnetic waves are transverse waves
which have both an electric and amagnetic effect.
Electromagnetic waves are unusual because they
do not need any substance to get from one placeto another.
They can travel through a vacuum.
Light andinfra-red radiation (heat) can reach theEarth
from the Sun through the vacuum of space.

When is Electromagnetic Radiation a Particle and when is it a Wave?

It is not true that electromagnetic radiation
is sometimes a particle and sometimes a wave.
It always has the properties of being botha particle and a wave.
This site will mostly talk about electromagnetic radiationas waves
but you need to know a little about it being particlestoo.

What is a Photon?

When thought of as particles
electromagnetic radiation is often called a rayor a beam.
A ray or beam of electromagnetic radiationis made from particles
called photons. A photon is a packetof energy.
Different photons have different amountsof energy.

Three types of electromagnetic radiation
(ultraviolet, x-raysand gamma rays)
can form ionsbecause the photonshave enough energy
to remove an electronfrom an atomor molecule.
These three types are called ionising radiation and they can all cause significant damageto living cells.

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