Question

In a Michelson experiment for measuring speed of light, the distance travelled by light between two reflections from the rotating mirror is 4.8 km. The rotating mirror has a shape of a regular octagon. At what minimum angular speed of the mirror (other than zero) the image is formed at the position where a nonrotating mirror forms it?

Answer 1

In the given Michelson experiment

D= 4.8 km = $4.8\times {10}^8$ m

We know c = D $\frac{\omega N}{2\pi }$

$\Rightarrow w=\frac{2\pi c}{DN}$ rad /sec

= $\frac{c}{DN}$ rev/sec

=$\frac{3\times {10}^8}{(4.8\times {10}^3\times 8)}$

= $\left(7.8\right)\times {10}^3$ rev/sec