Dual Nature Of Light Question 160
Question: The energy that should be added to an electron to reduce its de Broglie wavelength from one nm to 0.5 nm is [KCET 2005]
Options:
A) Four times the initial energy
B) Equal to the initial energy
C) Twice the initial energy
D) Thrice the initial energy
Show Answer
Answer:
Correct Answer: D
Solution:
$ \lambda =\frac{\hbar }{\sqrt{2mE}} $ ; $ \frac{\lambda ‘}{\lambda }=\sqrt{\frac{E}{E’}} $ Þ $ \frac{E}{E}={{( \frac{0.5}{1} )}^{2}} $ Þ $ E’=\frac{E}{0.25}=4E $ The energy should be added to decrease wavelength. $ =E’-E=3E $
BETA
