AQA GCSE Red Shift (Physics)
Red shift
Stars emit light, which we receive on Earth.
If a star is moving away from us, the light that we receive from that star is red shifted, this means it will have more of a red tinge to the light. Look at the image below, do you notice that when the star is further from the Earth the wavelength of light emitted from the star is greater.
Visible light from stars contains all of the wavelengths of light. Red light has a longer wavelength than violet light as shown below.
So, red shifted light means that more of the wavelengths of light that we receive will be in the red end of the visible light spectrum. This will make the light appear with more of a red tinge.
Galaxies and Red shift.
Our universe is made up of billions of galaxies. Each galaxy is made up of billions of stars.
If a galaxy is moving away from us, the light we receive from them is red shifted.
Light is emitted from the stars, if the galaxy is moving away from us, the stars are also moving away from us.
Stars mostly contain hydrogen, below are two absorption spectra. Top one is for light would be received from a normal distance star, whilst the bottom one would represent light from a star moving away from us. The absorption lines in bottom spectrum have moved towards the red end of the visible light spectrum, showing a red shift.
Big bang basics
The big bang theory is a theory put forward to explain the origins of the universe.
It states that the universe started as as single concentrated point, then an explosion sent energy and matter outwards. Even today, this matter is moving outwards, so the universe is currently expanding. This means that galaxies are moving further away from us.
There is evidence for this:
1. The greater the distance between Earth and the galaxy, the greater the observed increase in wavelength and red shift of the light that we receive from these galaxies.
2. Big bang theory states that all matter started at a single point, so the more distant galaxies must had been moving faster to now be further away, this again is shown by a greater red shift and a greater observed increase in wavelength.
3.The observed red shift provides evidence that the universe is expanding and so it supports the Big Bang theory.
Practice Questions
1. Explain what is meant by the term red shift.
2. If a galaxy were moving towards us, how would this affect the light that we would receive from the galaxy.
3. How does the red shift provide evidence that the universe is expanding?
Absorption and Emission of EM Radiation
JJ Thomson and Plum pudding model
Ernest Rutherford and the Nuclear Model
Niels Bohr changing the Nuclear Model
Discovering the Proton and Neutron
Measuring radiation from radioactivity
Radiation types and properties
Random nature of radioactive decay
Radioactive contamination or irradiation
Hazards of contamination and irradiation
Studies on the effects of radiation on humans
Different half lives of radioactive isotopes
Nuclear Fission Chain Reaction
Writing nuclear fission equations
Drawing ray diagrams for a concave lens
Drawing Ray Diagram to produce a virtual image for a convex lens
Drawing ray diagram to produce a real image for a convex lens.
Specular and Diffuse Reflection
Seeing Coloured Objects Part 2
Viewing objects through coloured filters
Transparent, Translucent and Opaque