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. $
