Electromagnetic Waves

Electromagnetic Waves:

• Can travel through a vaccum
• Created by vibrating electric and magnetic fields
• Travel at the speed of light

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• Gamma rays                                     Smallest
• X rays
• Ultraviolet
• Visible light
• Infrared
• Microwaves
• Radio waves
• Long, medium & short waves             Biggest

Additive light                                                   Total internal reflection

                                                                      If light enters at an incident angle more than the                                                                      'critical angle', it is totally internally reflected.

Blue filter:

• Transmits blue (lets blue light through)
• Absorbs all other colours

Yellow filter:

• Transmits yellow & green light
• Absorbs all other colours

Film cameras: Use chemicals to project the image

Digital cameras: Use electrical charges to process the image

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Infrared Light:

• TV remote controls
• Cameras to detect people in smokey rooms

Optical fibres:

• Trap light & information as pulses of light that can be sent along these fibres
• Can carry more information than electrical wires
• There is no interference, costs more and absorbs less energy

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Producing Radiowaves:

• When the electron moves, waves are created
• The waves oscillate and reach teh recievers electrons, creating an electrical signel
• Microwaves can penetrate through the atmosphere and reach satellites. Radiowaves cannot

Microwaves: Used for mobile phones, TV links and satellite TV

Radiowaves (Wavelength > 1m): Used for TV broadcasting, carry more information

Radiowaves (Wavelength between 1m and 100m): Used by radio stations, range is limited

Radiowaves (Wavelength < 100m): Used by national and international radio stations

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Microwaves:

• Can beam information from mast to mast
• Aren't diffracted much by the environment
• Travel in straight lines

Doppler effect:

• Red shift: Waves are moving AWAY, higher wavelength, lower frequency. Light becomes more reddish
• Blue shift: Waves are moving TOWARDS, lower wavelength, higher frequency. Light becomes more blueish
• The larger the red/blue shift, the faster the object is moving

• The further away a galaxy, the faster it is moving away from us
• If everything is moving away from us now, then maybe everything was closer together in the past
• Maybe everything came from a single point and has been EXPANDING ever since

This is the Big Bang Theory

CMBR: Cosmic Microwave Background Radiation- the radiation given off by the big bang

Dark matter: this accounts for 90% of the universe's mass ('creating' gravity). Dark matter doesnt give out radiation, so we cannot see it.