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?
Distance travelled by the light wave between two reflections from the rotating mirror (D) = 4.8 km = 4.8 × 103
Number of faces of the mirror, N = 8
The angular speed of the mirror = ω = ?
In the Michelson experiment, the speed of light (c) is given by;
Therefore, we can write ω as,
The angular velocity of the mirror in terms of rev/s
Hence the required angular velocity of the mirror is 7.8 × 103