Question

The number of photons emitted in 10 hours by a 60 W sodium lamp are:

($\lambda$ of photon = 6000$\stackrel{\text{o}}{\text{A}}$)

• A. $\text{6}\text{.52}\times {\text{10}}^{\text{23}}$
• B. $6.40\times {10}^{23}$
• C. $8.40\times {10}^{23}$
• D. $3.40\times {10}^{23}$

Answer 1

The correct option is A $\text{6}\text{.52}\times {\text{10}}^{\text{23}}$

Power=60w

Time=10 hours=10$\times 3600$sec$=3.6\times {10}^4$sec

Energy=power$\times$time

$\Rightarrow Energy=2.16\times {10}^{6}J$

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

given $\lambda =6000\stackrel{0}{A}$

energy of 1 photon =$\frac{6.626\times {10}^{-34}\times 3\times {10}^8}{600\times {10}^{-10}}$

where $h=$Planck constant $=6.626\times 10-34J$;

$c=$speed of light $=3\times {10}^8$

$\therefore energyof1photon=3.313\times {10}^{-18}Joules$

Now, no of photons$=\frac{energy}{energyof1photon}$

$=\frac{2.16\times {10}^6}{3.313\times {10}^{-18}}$

$=6.52\times {10}^{23}$photons

Hence, the correct option is $\left(A\right)$