P1 - EM Waves Flashcards
What are all the wave types in the electromagnetic spectrum in order? Give their wavelengths
Radio (1m to 10^4m)
Microwaves (10^-2m)
Infrared (10^-5m)
Visible light (10^-7m)
Ultraviolet (10^-8m)
X-rays (10^-10m)
Gamma rays (10^-12m)
What is the electromagnetic spectrum?
The continuous group of wave types that are all transverse and travel at the speed of light
Decreasing the wavelength would bring you up in the electromagnetic spectrum
What are radio waves used for?
Communication including TV and FM radio transmissions
How are long radio waves sent to their destination?
They can diffract around hills and other similar obstacles so you don’t need a direct line of sight
How are medium-length radio waves sent to their destination?
They bounce off the ionosphere (electrically charged layer of the atmosphere) to get to their destination
How are short radio waves sent to their destination?
You have be in a line of sight of the transmitter to receive the very short radio waves
Which type of wave is used for FM radio and TV?
The very short wavelength radio waves
In communication, what are microwaves used for?
Satellite communication and mobile phones
Why are microwaves used for satellite communication instead of radio waves?
The wavelength has to be short enough to pass through the Earth’s watery atmosphere to get to the satellites
Describe how a satellite TV or mobile phone signal would travel to its destination
The transmitter would transmit the signal into space where it would be picked up by a satellite
The satellite would then transmit the signal to the TV or mobile phone
Why are people worried about how taking mobile phone calls could be dangerous to us?
If microwaves are travelling somewhere and they go through some water, the water would absorb them and then be heated up
If we hold a mobile phone close to our head while taking a call, the microwaves could be cooking the water in our cells and possibly damaging us
How do remote sensing satellites work?
Microwaves are used by the satellites to see through the clouds in order to monitor oil spills, icebergs etc.
Give 2 ways in which infrared waves are used for communication
Sent by remote controllers in patterns to give instructions
IR and visible light are used to carry data over optical fibers by bouncing off the sides of the fibre
Describe how a camera works
Use a lens to focus visible light onto a light sensitive film or electronic sensor
The lens aperture controls how much light enters the camera (like a pupil)
The shutter speed determines how long the film or sensor is exposed to light
Varying the shutter speed and aperture can decide how much light is in a photo
