Question

The energy of a photon of light of wavelength 450 nm is

• A. $4.4\times {10}^{-19}J$
• B. $2.5\times {10}^{-19}J$
• C. $1.25\times {10}^{-17}J$
• D. $2.5\times {10}^{-17}J$

Answer 1

Answer: (A)

. $4.4\times {10}^{-19}J$.

The energy ($E$) associated with an electromagnetic wave having wavelength ($\lambda$) is given by,

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

where,

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

$c=3\times {10}^8=Speedoflightinvacuum$

$\Rightarrow E=\frac{hc}{\lambda }=\frac{6.62\times {10}^{-34}\times 3\times {10}^8}{450\times {10}^{-9}}=4.4\times {10}^{-19}J$.