Question

The number of photons of light of wavelength $7000\mathring{A}$ equivalent to $1J$ are

• A. $3.52\times 10^{-18}$
• B. $3.52\times 10^{18}$
• C. $50,000$
• D. $10,0000$

Answer 1

Answer: (B)

$E=\frac{nhc}{\lambda }$
$n=\frac{\lambda \times E}{h\times c}=\frac{7000\times 10^{-10}m\times 1J}{6.6\times 10^{-34}J-s\times 3\times 10^{8}m/s}$