Turning Points: Special Relativity

Question 1

Outline the experimental procedure and the arrangement of the Michelson-Morley experiment.

Answer 1

→ monochromatic light is split into two using beam splitter (partially reflective surface)
→ split beams travel perpendicularly towards two mirrors set up at same distance from splitter
→ plane block ensures both beams pass through same thickness of glass
→ reflected beams have a path difference & combine to form interference pattern

Question 2

Explain the expected result of the Michelson-Morley experiment.

Answer 2

→ rotating apparatus by 90° would cause a shift in
the interference pattern
→ light moving parallel to Earth would take longer

Question 3

Explain the conclusions drawn from the Michelson-Morley experiment.

Answer 3

→ no shift in interference pattern
→ no ether
→ speed of light is invariant in free space

Question 4

State the measurements made and the observation that provides evidence for relativistic
time dilation.

Answer 4

→ place one detector at high altitude & one much further down to measure change in muon count rate
→ measure no. of muons that pass through per second
→ fewer muons decay than expected therefore half-life appears longer

Question 5

When can the theory of special relativity not be applied?

Answer 5

when there is acceleration

Question 6

State what is meant by an inertial frame of reference.

Answer 6

one which moves at a constant velocity relative

Question 7

State Einstein’s two postulates.

Answer 7

• speed of light is invariant in free space
• laws of physics have the same form in all inertial frames