Red shift occurs when the wavelength of electromagnetic waves, such as light from distant stars, appears longer than normal, indicating the star is moving away from the observer. The greater the red shift, the faster the star is receding due to the expansion of the universe, with more distant galaxies exhibiting larger red shifts.

1. What is Red Shift?

2. Important To make this model easier to understand sound waves will be drawn as transverse waves. We know that sound waves are really Longitudinal waves . This error is intentional !

3. Police Car standing still Waves emitted have a normal wavelength.

4. Police car approaches Wavelengths now appear shorter than normal. Sound has a higher pitch.

5. As Police car moves away Waves appear longer than they normally are. This gives a deeper sound.

6. Apparent change in wavelength from moving objects . This is called the Doppler Effect. Electromagnetic waves from distant stars behave in the same way. We can use this principle to tell if they are approaching or moving away.

7. Summary If an electromagnetic wave appears longer than it should be, then it has been red shifted .The object must therefore be moving away. The more the red shift , the faster it is moving away.

8. Extension From the model you can guess that if stars are approaching us ,their light would appear to be blue shifted. Astronomers have found that the more distant the galaxy, the more red shift they observe. The universe appears to be expanding at a greater rate ,the further out you go.