Dual Nature Of Light Question 121
Question: The eye can detect 5 ´ 104 photons per square metre per sec of green light (l = 5000 Å) while the ear can detect $ {{10}^{-13}},(W/m^{2}) $ . The factor by which the eye is more sensitive as a power detector than the ear is close to
Options:
A) 5
B) 10
C) 106
D) 15
Show Answer
Answer:
Correct Answer: A
Solution:
$ E=\frac{12375}{5000}=2.475,eV,\approx 4\times {{10}^{-19}}J $ So the minimum intensity to which the eye can respond $ I_{Eye}= $ (Photon flux) ´ (Energy of a photon) Þ $ I_{Eye}=(5\times 10^{4})\times ,(4\times {{10}^{-19}})\tilde{}2\times {{10}^{-14}},(W/m^{2}) $ Now as lesser the intensity required by a detector for detection, more sensitive it will be $ \frac{S_{Eye}}{S_{Ear}}=\frac{I_{Ear}}{I_{Eye}} $ $ =\frac{{{10}^{-13}}}{2\times {{10}^{-14}}}=5 $ i.e. as intensity (power) detector, the eye is five times more sensitive than ear.
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