Question

In Fizeau method of measuring the speed of light, the toothed wheel is placed in the focal plane of a converging lens. How would the experiment be affected if the wheel is slightly away from the focal plane?

Answer 1

Fizeau method:

• This experiment is used to find the speed of the light relative to moving water.
• It measures the medium movement upon the light speed.
• When the toothed wheel is slightly moved away from the focal plane of a converging lens then the returning light will fall on the extended area of the wheel.
• When it is moved away, the image will appear even when one of the teeth of the wheel is blocked from the light.

Answer 2

If the wheel is positioned away from the focal plane, the light returning light rays fall into the extended area of the wheel this will let picture appear even when one of the wheel's teeth blocks the light ray.

Explanation:

Measuring the speed of light :

Radio or light wave contact is constrained by the velocity with which the waves will travel.    

For example, signals sent to the Pioneer 10 deep space probe currently take five hours to reach the spacecraft from Earth, so corrections to the course must be sent at least five hours before necessary! Knowledge of the importance of light speed in astronomy is critical when calculating the light year.

The main problem with the calculation of light speed is its very high value, hence we must use very large distances or very precise methods of timing. Most of the methods to be mentioned here are based on the short bursts of the light; the way they do this differs from experiment to experiment.