Question

Calculate the energy in joule corresponding to light of wavelength 45 nm.
$\text{(Planck's constant},h=6.63\times {10}^{-34}J.s,\text{speed of light},c=3\times {10}^{8}m.s^{-1})$

• A. $6.67\times {10}^{15}$
• B. $6.67\times {10}^{11}$
• C. $4.42\times {10}^{-15}$
• D. $4.42\times {10}^{-18}$

Answer 1

The correct option is C $4.42\times {10}^{-15}$

$E=\frac{hc}{\lambda }\lambda =45\times {10}^{-9}m$
Putting the values in equation:
$E=\frac{6.63\times {10}^{-34}J.s\times 3\times {10}^{8}m.s^{-1}}{45\times {10}^{-9}m}E=4.42\times {10}^{-18}J$