Problem 4.2: At time t = 0 a laser, mounted on a wall and stationary in Frame S, fires a pulse of light straight
across the room to a mirror fixed on the opposite wall a distance L. It is reflected straight back.
Fix the origin of the reference Frame S at the laser's position at time ct = 0, the length L extending out along the
x-axis (with it's left end at the origin). The light pulse leaves the origin at 0.
(a) Draw the Minkowski diagram of the world line of the light pulse for the complete trip to the mirror and back.
Label the pulse's origin A, the reflection event B and it's return to the source C. What are the coordinate values
(x, t) of each event A, B, and C in the S inertial system?
(b) Draw the coordinate axes of an inertial system S' that moves to the right with a velocity v = 3c/5. Mark on the
ct' axis the time each event occurs in the S' system.
(c) In the S' system the trip to the wall and the trip back from the wall take the same amount of time
$\Delta t_{AB} = \Delta t_{BC}$. Is that true in the S' system? From your drawing, estimate the ratio of the time $\Delta t'_{BC}/\Delta t'_{AB}$.
