Question

Find the number of photons emitted per second by a 24 W source of monochromatic light of wavelength 6600 $\stackrel{{}^{\circ }}{A}$ :

• A. $8\times {10}^{19}$
• B. $4\times {10}^{19}$
• C. $2\times {10}^{19}$
• D. $1\times {10}^{19}$

Answer 1

The correct option is A

$8\times {10}^{19}$

$P=\frac{nhc}{\lambda }$

$24=\frac{n\times 6.6\times {10}^{-34}\times 3\times {10}^8}{6600\times {10}^{-10}}$

$\therefore n=8\times {10}^{19}$