P1 - Electromagnetic Waves Flashcards
What are EM waves?
Electric and magnetic disturbances that transfer energy.
What are the parts of the EM spectrum?
- Radio
- Microwave
- IR
- Visible Light
- UV Radiation
- Gamma radiation and X-Rays
What is the speed of an EM wave?
300,000,000 ms^1
How does the energy of an EM wave change with its frequency?
The higher the frequency, the higher the energy.
Which EM waves have the highest energy?
Gamma rays because they have the shortest wavelength.
What is white light?
White light contains all the colours of the spectrum.
What is IR used for?
Carrying signals from remote devices and inside optical fibres.
What are microwaves used for?
Carrying satellite TV programmes and mobile phone calls.
What are radio waves used for?
Radio and TV broadcasting, radio comms and mobile phone calls.
What are the hazards of light, infrared, micro and radio waves?
Microwaves and radio waves cause internal heating.
IR causes skin burns.
Why are microwaves used to beam signals long distances?
Microwaves don’t spread out as much as radio waves.
What is the range of radio wave frequencies?
300kHz - 3GHz
Give a specific use of radio waves.
Bluetooth allows devices to connect up to ten metres away without cables.
Why are different wavelength radio waves used for different purposes?
The wavelength affects:
- how far the wave can travel.
- how much the waves spread.
- how much info. a wave can carry.
Which type of wave is used for satellite TV?
Microwaves.
What are optical fibres?
Thin, transparent fibres that transmit signals using light and IR.
How are radio waves emitted from an aerial?
Alternating voltage through the aerial. The frequency of the radio wave is the same as the wave of alternating voltage.
How do aerials receive data?
When the incoming radio waves passes across the aerial, an alternating voltage is produced which is connected to a speaker, producing sound waves.
Give two advantages of fibre optic communications.
- More info. can be carried due to the much smaller wavelength.
- More secure because the signal stays within the fibre.
What is red shift?
The shift to longer wavelengths of the light from it be use the object is moving away.
How does red-shift depend on speed?
The faster a galaxy is moving away, the greater its redshift.
What evidence is there of distant galaxies moving away from Earth?
All distant galaxies show redshift. The further away the galaxy is, the greater its redshift.
What is the Doppler effect?
The change in observed wavelength due to motion of the source of the wave.
Give two examples of the Doppler effect.
A train going past a station (sound).
Redshift (light).
