Electromagnetic Waves Flashcards
What are electromagnetic waves?
Transverse waves that transfer energy from their source to the absorber
Different substances may transmit, reflect or refract EM waves that vary with wavelength
Refraction occurs when there is a difference in the velocity of an EM wave in different substances
What do EM waves form?
A continuous spectrum
Grouped by wavelengths and frequencies
Travel at same speed through air/ a vacuum
3 x 10^8 m/s
What is the shortest wavelength and longest wavelength of EM waves?
Below 10^-15
Above 10000m
What is the order of electromagnetic waves?
Radio
Micro
Infrared
Visible
Ultraviolet
X rays
Gamma rays
How do ray diagrams show refraction?
If a wave slows down, it will bend towards the normal
What are wave front diagrams?
Explain refraction in terms of change in speed
Imaginary line at right angles to the direction the wave is moving
If a wave slows down, the wave fronts become closer
One end of the wave front changes speed before the other so the wave changes direction
What are properties of EM waves?
Wide range of frequencies absorbed or produced by changes inside a nucleus
When electrons move down energy levels, they emit EM waves
What are uses of EM waves?
Can have hazardous effects
Radiation dose = risk of harm from exposure of the body to a particular radiation
What are properties of radio waves?
Oscillations in an electrical circuit
When absorbed by a receiver aerial, may create an AC with the same frequency as radio waves
What are radio waves?
Television and radio signals
Travels long distances through air
Longer wavelengths bend around obstructions to allow detection of signals
Can penetrate body and cause internal heating
What are microwaves?
Satellite communication and cooking food
Can pass through Earths atmosphere and penetrate into food and absorbed by water molecules in food, heating it
Can penetrate the body and cause internal heat
What are infrared waves?
Electrical heaters, cooking food, infrared cameras
Sensors detect infrared waves emitted by hot object and turn into image
Can transfer energy quickly
Can damage or kill skin cells due to heating
What is visible light?
Fibre optics communication
Short wavelength means visible light carries more information
Can damage retina
What is ultraviolet light?
Energy efficient lights and artificial sun tanning
Some chemicals inside light bulbs can absorb UV and emit visible light
Carry more energy than visible light
Can damage skin cells, causing premature skin aging and skin cancer or blindness
What are X rays and gamma rays?
Medical imaging and treatments
Pass easily through flesh but not dense material like bone
High doses kill living cells so can be used to kill cancer cells or harmful bacteria (gamma)
Form of ionising radiation which can cause mutation
