Electromagnitic Waves Flashcards
All electromagnetic waves travel at the same _________
Speed
What are electromagnetic radiations
Electric and magnetic disturbances
Electromagnetic waves have different _______ and ________
Wavelengths
Frequencies
Which electromagnetic wave has the shortest wavelength but the highest frequency
Gamma
Which waves have the longest wavelength but the lowest frequency
Radio waves
In terms of energy, what does a higher frequency of a wave mean
The more energy it transfers
What are microwaves used for
Communications
Why are microwaves used to transmit signals to satellites
Microwave transmitters produce wavelengths that are able to pass though the earths atmosphere
What are radio waves used to transmit
Radio, TV, programmes and mobile phone signals
Why are microwaves and radio waves bad for your health
They penetrate your skin and are absorbed by body tissue, this can heat internal organs and may damage them
Why is infrared radiation bad for your health
It is absorbed by the skin and causes burns to the skin
Why is the radio and microwave spectrum split up into bands
Different bands are used for different communication purposes
How are radio waves produced
By applying an alternating voltage to an
The shorter the wavelength of an electromagnetic wave, _____ information they carry
More
What are optical fibres
They are very thin glass fibres
What are glass fibres used to transmit
Signals carried by invisible light or infra red
How do light signals travel through an optical fibre
They are totally internally reflected
Why are optical fibres better than radio or microwaves
- carry more information
- more secure
What is the Doppler effect
The change in the observed wavelength
What happens to the wave when the source moves away from the observer
The observed wavelength decreases and the frequency increases
What are galaxies
A large collection of stars
If an object is moving away from you then it has _____ shift
Red
If an object is moving closer to you it is called _____ shift
Blue
How does red shift show the universe is expanding
The furthest galaxies are moving the fastest so everything is expanding outwards
What is the Big Bang theory
The theory that the universe began with a massive explosion from a small initial point
What is the proof of the Big Bang
Cosmic microwave background information
What is a galaxy
A large collection of stars
What has happened to the frequency of light that reaches earth from distant galaxies
It has shifted towards the red end of the spectrum
How can we tell if light from a distant galaxy has been red shifted
By observing the black lines on a spectrum
