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Electromagnetic Waves - C13 - Coggle Diagram
Electromagnetic Waves - C13
EM Spectrum
All EM waves are transverse waves that transfer energy from a source to an absorber
A hot object transfers infrared radiation which is absorbed by the surroundings, heating them up
All EM waves have the same speed through air or a vacuum
EM waves form a continuous spectrum through a range of frequencies
They are grouped into seven basic types based on wavelength and frequency
There is a large frequency because EM waves form by a variety of changes in atoms and their nuclei
E.g. Changes in the nucleus of an atom forms gamma radiation
Because of their different properties, EM waves are used for various different things
Refraction
When a wave crosses a boundary between materials at an angle it changes direction
How much the wave is refracted depends on whether the wave speeds up or slows down, which typically depends on the density of the two materials
If a wave hits a boundary and slows down, it will normally bend towards the normal (straight line)
If a bend hits a boundary and speeds up it will bend away from the normal
The
optical density
of a material is a measure of how fast light travels through it
Constructing a Ray Diagram
First start with a boundary line between two materials and a normal (line 90⁰ to the boundary)
Draw an incident ray that meets the normal at the boundary - The angle between the ray and the normal is the angle of incidence
Draw the refracted ray on the other side of the boundary
If the second material is optically denser than the first, the refraction line will bend towards the normal, on the other hand if it is optically less dense, the refraction line will bed away from the normal
If it bends towards the normal, the angle of incidence will be smaller and if it bends away from the normal the angle of incidence will be larger
Uses of EM waves
Light
Film cameras
Digital camera or mobile phone camera
lighting
Infrared
TV remotes
Infrared scanners
Infrared cameras
Microwaves
Communications such as satellite TV
Microwave ovens to cook food
Microwaves cook food by penetrating the food and being absorbed by the water molecules, heating the food up
Radio Waves
Carrying radio, TV and mobile phone signals
