Speed of light and relativity

Question 1

The Michelson-Morley interferometer

Answer 1

1. Monochromatic light sent towards a partial reflector
2. The light splits into two beams travelling at right angles to each other.
3. The beams are reflected at two mirrors (the second glass block on one of the paths is to make sure both beams of light travel through the same amount of air and glass)
4. When the reflected beams meet back at the partial reflector, the form an interference pattern
5. Which is recorded by the observer.
6. The whole interferometer is rotated through 90degrees and the experiment is repeated.

They expected there to be a change in interference pattern.
They did not get this result and it was always the same no matter when and where repeated.
Concluded:
- It is impossible to detect absolute motion - ether does not exist.
- Speed of light has the same value for all observers (speed of light is invariant).

Question 2

Einsteins Postulates

Answer 2

• Physical Laws have the same form in all inertial frames
• Speed of light in free space is invariant.