Question

Minimum number of photons of light of wavelength $4000\mathring{A}$, which provide 1 J energy.

• A. $2\times {10}^{18}$
• B. $2\times {10}^9$
• C. $2\times {10}^{20}$
• D. $2\times {10}^{10}$

Answer 1

The correct option is A $2\times {10}^{18}$

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

$n=Numberofphotons$

$h=Planc{k}^{\prime }sconstant=6.62\times {10}^{-34}Js$

$c=Speedoflight=3\times {10}^{8}m/s$

$\lambda =wavelengthoflight$

$n=\frac{1\times 4000\times {10}^{-10}}{6.62\times {10}^{-34}\times 3\times {10}^8}$

$n=2\times {10}^{18}$

So, the correct option is $A$