Electromagnetic waves are electrical and magnetic disturbances that transfer energy from one place to another.
There are 6 electromagnetic waves that go from low frequency to high frequency and the lower the frequency of the wave the bigger the wavelength and vive versa.
The electromagnetic waves in order from low frequency to high frequency are: radio -> microwave -> infa-red -> light -> ultraviolet radiation -> X-rays and gamma rays
Describing waves: A wave can transfer energy without transferring matter. The energy they transfer depends on wavelength of the waves. This is why waves of different wavelengths have different effects.
Theamplitudeof the wave is theheight of a wavefrom the middle to the top of the wave.
Thelambaof the wave is thewavelength of the wave, the distance from a pint on 1 wave to the same point on the net wave.
Thefrequencyof the wave is thenumber of complete waves passing a point each second / it is 1 second divided by the time of the wave
thetimeof the wave is thetime for 1 wave to pass a point / 1 second divided by the frequency of the wave
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Electromagnetic spectrum continued
Example of question on waves: A surfer sees 10 waves go past him in 5 seconds, and the wavelength of the waves are 3m. What is the speed of the wave.
speed = distance/ time
Thedistanceof the waveis 3m,thetime of 1 waveis 5 seconds divided by 10 ( which is equal to0.5 seconds) therefore the speed of the wave is3m/0.5s = 6m/s
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Speed of electromagnetic waves
All electromagnetic waves travel at speed of 300 millions m/s through space or in a vacuum = distance wave travel each second
wave speed (m/s) = frequency (Hz) X wavelength (m)
Example: A mobile phone gives out electromagnetic waves of frequency 900 illion Hz. Calculate the wavelength. Speed of elctromagnetic wave = 300 million m/s
Radio: A metal aerial will have an electric current created in it that changes at the same frequency as the radio wave is absorbed.
Speed: 300 million m/s
Frequency: 300 000 Hz to 300 million Hz
Wavelength: 100km to 1 mm
What transmits radio waves: music pictures, broadcasting, mobiles, Blue-tooth, wi-fi, sky TV, clocks
Radio waves side effects: possible risk of cancer
Reducing exposure of radio waves: moving away from the transmitter
Radio waves used as: television signals, GPS, wi-fi
Radio waves are emitted from an aerial when we apply an alternating voltage to the aerial. The frequency of radio waves produced are same as frequency of alternating voltage.
When radio waves pass across a receiver aerial, they cause a tiny alternating voltage in the aerial. The frequency of the alternating voltage is the same as the frequency of radio waves received.
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