Question

The eyes of certain member of the repltile family pass a single visual signal to the brain when the visual receptors are stuck by photons of wavelength 13.6nm. If a total energy of $3\times {10}^{-14}$ J is required to trip the signal, the minimum number of photons that must strike the receptor are:

• A. 20,000
• B. 22,000
• C. 25,500
• D. 30,000

Answer 1

Answer: (A)

Let n photon is required.
$E=nhv;n=\frac{3\times {10}^{-14}}{\frac{6.6\times {10}^{-34}\times 3\times {10}^8}{13.6\times {10}^{-9}}}=20,000$