Q216 · Practice questionComplex familiar1 mark
QUESTION 216
A monochromatic beam has fixed power , and its photons each have energy . Its frequency is doubled while its power stays fixed. What happens to the number of photons arriving per second?
(A)
It doubles.
(B)
It halves.
(C)
It remains unchanged.
(D)
It becomes four times as large.
WORKED SOLUTION
1 markAnswer B
ANSWER
B. It halves.
Worked solution
The photon rate is . Doubling frequency doubles energy per photon, so the same energy delivered each second corresponds to half as many photons.
Equivalent physically justified methods and consistent equivalent units accepted.
Displayed decimals are model answers; accept appropriate significant figures and consistent rounding from stated constants.
Select B.
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