JEE PYQ: Wave Optics Question 3
Question 3 - 2021 (18 Mar Shift 2)
The speed of electrons in a scanning electron microscope is $1 \times 10^7$ ms$^{-1}$. If the protons having the same speed are used instead of electrons, then the resolving power of scanning proton microscope will be changed by a factor of:
(1) 1837
(2) $\frac{1}{1837}$
(3) $\sqrt{1837}$
(4) $\frac{1}{\sqrt{1837}}$
Show Answer
Answer: (1)
Solution
Resolving power (RP) $\propto \frac{1}{\lambda}$
$\lambda = \frac{h}{p} = \frac{h}{mv}$
So (RP) $\propto \frac{mv}{h}$
RP $\propto P$
RP $\propto mv$
RP $\propto m$
Since $m_p = 1837 m_e$, resolving power changes by a factor of 1837.
BETA
