Optics Question 300
Question: The 21 cm radio wave emitted by hydrogen in interstellar space is due to the interaction called the hyperfine interaction is atomic hydrogen. the energy of the emitted wave is nearly
[CBSE PMT 1998]
Options:
A) $ {{10}^{-17}} $ Joule
B) 1 Joule
C) $ 7\times {{10}^{-8}} $ Joule
D) $ {{10}^{-24}} $ Joule
Show Answer
Answer:
Correct Answer: D
Solution:
$ E=\frac{hc}{\lambda }=\frac{6.6\times {{10}^{-34}}\times 3\times 10^{8}}{21\times {{10}^{-2}}} $ = $ 0.94\times {{10}^{-24}}\approx {{10}^{-24}}J $
