tutorial 2 v2.pdf - Name: Student Number: PHYS 200 TUTORIAL...

Name:
Student Number:
PHYS 200 TUTORIAL 2
For this tutorial, we’re going to derive the formulae for the special relativistic e ff ects called
“time dilation” and “length contraction”.
The “Principle of Relativity”, and specifically the postulate that the speed of light is the
same in all frames of reference, has immediate consequences for measurements of space and
time in di ff erent frames. As you will see, observers in relative motion will not generally
agree on distances or time intervals.
Recall that we have already showed that distances perpendicular to the direction of
motion (i.e. the y -axis in the “standard configuration”) are the same in the di ff erent frames.
But this will not be true of distances measured along an axis pointing in the direction of
motion (i.e. the x -axis).
Question 1 : Consider a simple apparatus consisting of two
parallel mirrors separated by a distance L . A pulse of light is
reflected back and forth between the two mirrors, as shown
in the figure.
Question 1(a) : In the frame attached to the mirrors, how
long does it take for the light to go from the bottom mirror
to the top mirror and back?
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