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The velocity of an electromagnetic wave in free space depends on the nature of the source that emits it. Which statement is correct?

1. It becomes larger as we go from gamma rays to radio waves
2. It becomes smaller as we go from gamma rays to radio waves
3. It remains identical for all such waves
4. None of the above

Correct answer: It remains identical for all such waves

Solution

In free space every electromagnetic wave (gamma rays to radio) propagates at the same speed c = 3x10^8 m/s, independent of frequency or source. So the speed remains identical for all such waves.

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