Unit 1: 6 - Electromagnetic Waves Flashcards
What are electromagnetic radiations?
Electric and magnetic disturbances.
What approximate wavespeed do all electromagnetic waves travel through a vacuum at?
300,000,000 m/s.
What electromagnetic waves have the shortest wavelength and highest frequency?
Gamma.
What electromagnetic waves have the longest wavelength and lowest frequency?
Radio waves.
How small wavelengths can gamma rays have?
10^-15m.
How large wavelengths can radio waves have?
1-10km.
Give an example of a device that uses visible light.
A camera.
Give an example of a device that uses infrared radiation.
Remote controls (for TVs etc.).
Give an example of a device that uses microwaves (apart from the obvious…).
Satellites (and mobile phones) to provide mobile phone networks.
Give an example of a device that uses radio waves.
Radios, TV signal generators, phone transmitters.
Can microwaves and radio waves penetrate skin?
Yes (and they can burn you or damage internal organs).
The radio and microwave spectrum is divided into different…
Bands.
The shorter the wavelength, the ____ information they can carry.
more
The shorter the wavelength, the ____ they can spread out.
less
Give a possible health concern about using mobile phones.
Microwaves can heat the brain, which is rumoured to damage it and cause cancers.
What are optical fibres?
Very thin glass fibres which can carry visible light or infrared radiation.
By what process does the electromagnetic waves remain inside the optical fibres?
By repeated total internal reflection.
What is the advantages of using optical fibres? (2)
They can carry much more information and are more secure than infrared and microwave transmissions.
What is the Doppler Effect?
When the wave source is moving relative to the observer, the waves detected by the observer will have shifted from the original.
When the source moves away, the wavelength ____ and the frequency ____.
Wavelength: Increases;
Frequency: Decreases.
When the source moves towards the observer, the wavelength ____ and the frequency ____.
Wavelength: Decreases;
Frequency: Increases.
What is red-shift?
When the frequency of light has decreased, and the wavelength has increased, suggesting an object is moving away.
Galaxies further away have ____ red-shifts to those closer to us. What does this suggest?
bigger. This suggests that the universe is still expanding as the faraway galaxies are moving away from each other.
What is CMBR?
Cosmic Background Microwave Radiation is the leftover radiation produced by the Big Bang. Scientists suggest that this used to be high energy gamma radiation, but as the universe expanded it would have become lower energy radiation.
