GK
BIG BANG THEORY
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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Increases
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Decreases
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Stays the same
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None of the above
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Detailed explanation-1: -When source moves towards a stationary observer, the same number of waves are contracted between smaller distance, so effective wavelength decreases and frequency increases.
Detailed explanation-2: -Waves emitted by an object traveling toward an observer get compressed-prompting a higher frequency-as the source approaches the observer. In contrast, waves emitted by a source traveling away from an observer get stretched out.
Detailed explanation-3: -There is a general way to increase the frequency of light. It is Doppler Effect. You can keep the observer (target for photoelectrons) and move the source of light towards it. But it is not practical, because you will need very high relative velocity to have any considerable change in the frequency.