Chapter 15, Problem 8A

The path of light in a vertical 'light clock' in a high-speed spaceship is seen to be longer when viewed from a stationary frame of reference. Why, then, does the light not appear to be moving faster?

To determine

To Explain: The nature of the path of the light clock using the concept of the time dilation.

Explanation of Solution

Introduction:

Time dilation is defined as the decrease in the motion of clock hands when the observer is moving with respect to the clock.

According to the theory of the relativity, light does not appear moving faster than the clock. Second postulate of relativity states that speed of light is constant and independent of the relative motion of the source. The speed of light does not change. Thus, the reason of longer visibility of path of light in the light clock is because of the slowing down of the clock. This phenomenon is also called time dilation.

Conclusion:

Thus, the path of the light in a vertical “light clock” seems to be longer due to the time dilation of the clock.