An early method of measuring the speed of light makes use of a rotating toothed wheel. A beam of light passes through a slot at the outside edge of the wheel, as in Fig. travels to a distant mirror, and returns to the wheel just in time to pass through the next slot in the wheel. One such toothed wheel has a radius of 5.0 cm and 500 teeth at its edge. Measurements taken when the mirror was a distance L = 500 m from the wheel indicated a speed of light of 3.0 X 105 km/s. (a) What was the (constant) angular speed of the wheel? (b) What was the linear speed of a point on its edge?

Hrishant Goswami , 9 Years ago

Grade 10