GCSE Edexcel Physics 5.HT - Electromagnetic Waves
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1
What can happen when EM waves move from one medium to another?
The wave can be:
Transmitted
Absorbed
Reflected
Refracted
Transmitted
Absorbed
Reflected
Refracted
2
When a wave moves from one medium to another, the interaction that happens will depend on…
The wavelength of the wave
The material the wave is travelling through
The material the wave is travelling through
3
If an EM wave moves through a substance, the denser the substance…
The slower the wave
4
Dispersion in EM waves
Different wavelengths slow down by different amounts in the same material
So different wavelengths of light will refract by different amounts and seperate
Violet light is refracted the most
Red light is refracted the least
So different wavelengths of light will refract by different amounts and seperate
Violet light is refracted the most
Red light is refracted the least
5
Explain thermal equilibrium
When an object absorbs and emits thermal radiation at the same rate
It will remain at a constant temperature
It will remain at a constant temperature
6
When a body absorbs radiation at a larger rate than it emits…
It gets hotter and will emit more radiation
7
When a body absorbs radiation at a smaller rate than it emits…
It gets colder and will emit less radiation
8
What factors affect the temperature of the earth?
Earth absorbs thermal radiation from the sun
The earth emits its own thermal radiation into space
Gases in the atmosphere absorb and reflect/emit some of this radiation back to earth
The earth emits its own thermal radiation into space
Gases in the atmosphere absorb and reflect/emit some of this radiation back to earth
9
Compare the wavelengths of thermal radiation emited by the sun and by the earth
Surface of the sun is hotter than surface of the earth
Therefore, wavelength from sun has shorter wavelength (higher energy = higher frequency = lower wavelength)
Therefore, wavelength from sun has shorter wavelength (higher energy = higher frequency = lower wavelength)
10
Greenhouse effect and gases
Natural process that warms the earth’s surface.
Greenhouse gases: methane, carbon dioxide
Greenhouse gases: methane, carbon dioxide
11
How can radio waves be produced?
By an antenna with a high frequency AC power source.
12
What happens in the radio transmitting antena?
Charge oscillates up and down antenna
Producing radio waves
Producing radio waves
13
What happens in the radio receiving aerial?
Metal aerial absorbs radio waves
Creates an alternating current with the same frequency as wave
Creates an alternating current with the same frequency as wave