P1-Electromagnetic Waves Flashcards
What is CMBR and why does it provide evidence for the Big Bang?
Cosmic Microwave Background Radiation is electromagnetic radiation created just after the Big Bang.
CMBR can only be explained by the Big Bang Theory, therefore it acts as evidence supporting the Big Bang Theory.
What is the Big Bang Theory?
The theory that the universe started with a ‘Big Bang’; a massive explosion from a small initial point, and that the universe has been expanding ever since.
What is the Steady State Theory?
An alternative theory that suggests the Universe is expanding but as it does new matter is created therefore the overall appearance of the Universe never changes.
How was CMBR discovered?
In 1965 two scientists, Penzias and Wilson discovered CMBR accidentally when they could not account for a microwave signal coming equally from all directions which was preventing them from being able to complete their experiments.
What is red-shift?
For visible light red has the longest wavelength and violet the shortest.
If the wavelength has increased and the frequency decreased, this is called red-shift.
How does red-shift provide evidence that the universe is expanding?
The light from all the distant galaxies is red-shifted. This means all the distant galaxies are moving away from each other, so the whole universe is expanding.
The further away the Galaxy the bigger the red-shift, meaning the most distant galaxies are moving the fastest.
Explain the Doppler Effect.
Imagine a wave source is moving relative to an observer. The wavelength and frequency of the waves detected by the observer will have shifted from the original produced by the source.
This is called the Doppler Effect.
Explain an example of the Doppler effect.
A siren increases in frequency as it travels towards an observer and drops in frequency as it travels away.
The observer would hear the siren with a higher pitch as it travels towards them, but would hear a lower pitch as it travels away from them.
Firemen onboard the engine with the siren would not hear a pitch change, as the wavelength would not change for them.
Order the electromagnetic spectrum from lowest wavelength to highest.
What is the electromagnetic wave speed and how can their wavelength and frequency be calculated?
All electromagnetic waves travel though space at a wave speed of 300 million m/s.
V= f x λ
Describe the link between electromagnetic waves’ wavelength and frequency.
The shorter the wavelength , the higher the frequency.
The longer the wavelength, the lower the frequency.
The higher the frequency the more energy it transfers.
Electromagnetic radiation that arrives from the Sun to Earth can be:
- High energy infrared.
- Visible light- white light contains all the colours of the spectrum.
- Low energy ultraviolet.
Which electromagnetic waves are used for communication and how?
- Visible light is transmitted through optical fibres to send signals.
- Microwaves are used to send signals to and from satellites and within mobile phone networks.
- Radio waves transmit radio and TV programs and carry mobile phone signals.
What information can scientists find out about a galaxy when they measure the size of the red-shift the galaxy produces?
Distance from Earth and the speed that galaxies are moving at.
