Question

In a Michelson experiment for measuring speed of light, the distance traveled 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 non-rotating mirror forms it?

• A. $780$ $rev/s$
• B. $7800$ $rev/s$
• C. $690$ $rev/s$
• D. $7500$ $rev/s$

Answer 1

Answer: (B)

$7800$ $rev/s$

Minimum angular speed $f=\frac{c}{dN}$

$=\frac{3\times {10}^8}{4.8\times {10}^3\times 8}$
$=7812rev/s\cong 7800rev/s$