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2017 OCR Physics A Wiens displacement law. Am I misunderstanding?

I have posted the whole question but I am interested in views on part iv.

It seems to me that this part of the question would bewilder many students as the proposal (from a 'scientist') would be viewed as so preposterous that the student might think they do not understand the question.

Of course I might be completely misunderstanding the questions but if we are dealing with Water then we have a cold body (the universe at 2.9K from earlier in Q) heating a warm body (Water at somewhere from 273K to 373K).

Apparently the answer is 1E(-13) K per second heating?


wiens law Q.jpg
(edited 7 months ago)
Reply 1
You missed off some important information required to solve (iii) [intensity of microwave background radiation is 3×106 W m23 \times 10^{-6} \mathrm{~W~m^{-2}}.

I agree that part (iv) doesn't really make much sense, since the water will be radiating back into space at least as much energy as it gains from the microwave background. They try to fudge it by saying "maximum temperature rise", but this would require having an infra-red filter on the surface to prevent any heat radiation back into space which is also transparent to microwaves.
Reply 2
Original post by lordaxil
You missed off some important information required to solve (iii) [intensity of microwave background radiation is 3×106 W m23 \times 10^{-6} \mathrm{~W~m^{-2}}.

I agree that part (iv) doesn't really make much sense, since the water will be radiating back into space at least as much energy as it gains from the microwave background. They try to fudge it by saying "maximum temperature rise", but this would require having an infra-red filter on the surface to prevent any heat radiation back into space which is also transparent to microwaves.


agreed, thought I had captured whole question, not relevant to iv though.

the filter postulated is of course Maxwell’s devil.

There are a few awful questions in these physics papers.

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