Exam-style question
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Which of the following best defines proper time in special relativity?.
- A.Proper time is the time measured by a clock at rest relative to the event.
- B.Proper time is the time measured by a moving clock.
- C.Proper time is the time measured by a clock moving at the speed of light.
- D.Proper time is the time measured by a clock in a gravitational field.
Model answer
What a good answer should say
- Proper time is the time measured by a clock at rest relative to the event.
Explanation
Why this works
The time dilation formula is Δt = γ Δτ, where Δτ is the proper time. Proper time is therefore the time measured by a clock that is at rest with respect to the event being observed, and it is the smallest time interval between two events in any inertial frame.
Common mistake
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