Question

The eye can detect $5\times {40}^4$ photons $(m^{2}s{)}^{-1}$ of green light $(\lambda =5000\stackrel{o}{A})$, while ear can detect ${10}^{-13}W{m}^{-2}$. As a power detector, which is more sensitive and by what factor?

• A. Eye is more sensitive and by a factor of 5.00
• B. Ear is more sensitive by a factor of 5.00
• C. Both are equally sensitive
• D. Eye is more sensitive by a factor of ${10}^{-1}$

Answer 1

Answer: (A)

Eye is more sensitive and by a factor of 5.00

According to the given information the eye can detect the intensity

$I=nhv$

$=n\frac{hc}{\lambda }$

$=\frac{5\times {10}^4\times 6.63\times {10}^{-34}\times 3\times {10}^8}{5\times {10}^{-7}}$

$\approx 0.2\times {10}^{-13}W/㎡$

$\therefore$Eye can detect $5$ times smaller intensities than that of ear. So, Eye $5$ times more sensitive than ear.