Two clocks are located at the origins of the two reference frames Z and Z' related via the standard configuration. After time t, an observer at the origin of Z observes the Z' clock by means of a telescope. What does the Z' clock read? Note: you must take into account the signal from the Z' clock travels at the speed of light to get to an observer in Z.

Two clocks are located at the origins of the two reference frames Z and Z' related via the standard configuration. After time t, an observer at the origin of Z observes the Z' clock by means of a telescope. What does the Z' clock read? Note: you must take into account the signal from the Z' clock travels at the speed of light to get to an observer in Z.