17.1 Modern Physics: Relativity of Time

This online activity was used to help us understand the basic concepts of relativity. In these problems we will explore how space and time are distorted as different frames approach the speed of light. We will make use of the time dilation equation which is (delta)t' = (delta)t/sqrt[1-(v^2/c^2)]. Screenshots of each of the question a posted below with their corresponding answers.

Question#1: How does the distance traveled by the light pulse on the moving light clock compare to the distance traveled by the light pulse on the stationary light clock?

Answer: The distance traveled by the moving light clock is greater than the distance travel by the stationary light clock.


Question #2: Given that the speed of the light pulse is independent of the speed of the light clock, how does the time interval for the light pulse to travel to the top mirror and back on the moving light clock compare to on the stationary light clock?

Answer: Since the speed of light is constant, the moving light clock must travel a further distance and therefore must take more time to complete one cycle.

Question #3: Imagine yourself riding on the light clock. In your frame of reference, does the light pulse travel a larger distance when the clock is moving, and hence require a larger time interval to complete a single round trip?

Answer: In the moving frame of reference, the light pulse does not travel a greater distance, thus the time required for the light to make one cycle in the moving frame is the same time as the light to make one cycle in the stationary frame.

Question #4: Will the difference in light pulse travel time between the earth's timers and the light clock's timers increase, decrease, or stay the same as the velocity of the light clock is decreased?

 Answer: If the velocity of the light clock is decreased, the difference of earth's timer and the light clock's timers also decreases.

Question #5:  Using the time dilation formula, predict how long it will take for the light pulse to travel back and forth between mirrors, as measured by an earth-bound observer, when the light clock has a Lorentz factor (γ) of 1.2.

 Answer: The time dilation of a moving clock with a Lorentz factor of 1.2 will have a time 1.2 times that of the original time.

Question #6: If the time interval between departure and return of the light pulse is measured to be 7.45 µs by an earth-bound observer, what is the Lorentz factor of the light clock as it moves relative to the earth?

 Answer: The measured time is 7.45 µs, we used the simulator and found that the Lorentz factor is around 1.12, which is what about the same number we calculated.