Question

Assume that $2 \times 10^{-17} J$ of light energy is needed by the interior of the human eye to see an object. How many photons of yellow light with $\lambda=595.2\, nm$ are needed to generate this minimum energy?

• A. 6
• B. 30
• C. 45
• D. 60

Answer 1

Answer: (D)

$E=n \frac{h c}{\lambda} $
$\Rightarrow 2 \times 10^{-17}$
$=n \times \frac{6.626 \times 10^{-34} \times 3 \times 10^8}{595.2 \times 10^{-9}}$
$\Rightarrow n=60$