Exam-style question
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According to Einstein's postulate, what is the value of the speed of light in vacuum?.
- A.3.00 × 10^8 m/s in all inertial frames.
- B.3.00 × 10^8 m/s only in the rest frame of the source.
- C.3.00 × 10^8 m/s only in the rest frame of the observer.
- D.3.00 × 10^8 m/s only in the presence of gravitational fields.
Model answer
What a good answer should say
- 3.00 × 10^8 m/s in all inertial frames.
Explanation
Why this works
Formula/rule: constancy of the speed of light. Substitution: none.
Working: The second postulate states that the speed of light in vacuum is a universal constant, c ≈ 3.00 × 10^8 m/s, and it does not depend on the motion of the source or observer. Answer: c = 3.00 × 10^8 m/s in all inertial frames.
Units/conclusion: c = 3.00 × 10^8 m/s, same for all inertial observers.
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