Question

In the Fizeau experiment on measurement of the velocity of light the distance between the gear wheel and the mirror is l = 7.0 km, the number of teeth is z = 720. Two successive disappearances of light are observed at the following rotation velocities of the wheel: n₁ = 283 rps and n₂ = 313 rps. Find the velocity of light.

Answer 1

In the Fizean experiment, light disappears when the wheel rotates to bring a tooth in the position formerly occupied by a gap in the time taken by light to go from the wheel to the mirror and back. Thus distance travelled = 2l Suppose the m^th tooth after the gap has come in place of the latter. Then time taken