The eye can detect 5 ×1 | vedclass

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Question

(a) $E = \frac{{12375}}{{5000}} = 2.475\,eV\, \approx 4 	imes {10^{ - 19}}J$

So the minimum intensity to which the eye can respond

${I_{Eye}} =

Vedclass · Accepted Answer

$5$

Vedclass · Answer

(a) $E = \frac{{12375}}{{5000}} = 2.475\,eV\, \approx 4 	imes {10^{ - 19}}J$

So the minimum intensity to which the eye can respond

${I_{Eye}} = $ (Photon flux) $&times;$ (Energy of a photon)

$&rArr;$ ${I_{Eye}} = (5 	imes {10^4}) 	imes \,(4 	imes {10^{ - 19}})	ilde --2 	imes {10^{ - 14}}\,(W/{m^2})$

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 	imes {{10}^{ - 14}}}} = 5$ i.e. as intensity (power) detector, the eye is five times more sensitive than ear.

The eye can detect $5 ×10^4$ photons per square metre per sec of green light ($\lambda$ $= 5000\ \mathop A\limits^o $) 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

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