NEET Solved Paper 2014 Question 2

Question: Calculate the energy in joule corresponding to light of wavelength 45 nm : (Planck’s constant $ h=6.63\times {10^{-34}} $ Js; speed of light $ c=3\times 10^{8}m{s^{-1}}) $ [AIPMT 2014]

Options:

A) $ 6.67\times 10^{15} $

B) $ 6.67\times 10^{11} $

C) $ 4.42\times {10^{-15}} $

D) $ 4.42\times {10^{-18}} $

Show Answer

Answer:

Correct Answer: D

Solution:

The wavelength of light is related to its energy by the equation,

$ E=\frac{hc}{\lambda }. $ Given, $ \lambda =45nm=45\times {10^{-9}}m $ $ [\because ,1nm={10^{-9}}m] $

Hence, $ E=\frac{6.63\times {10^{-34}}js\times 3\times 10^{8}m{s^{-1}}}{45\times {10^{-9}}m} $ $ =4.42\times {10^{-18}}J $

Hence, the energy corresponds to light of wavelength 45 nm is $ 4.42\times {10^{-18}}J. $