Question

21. Potential difference required to produce electrons
of wavelength 5Å in an electron microscope will
be :-
(1) 2.5 V (2) 6 V (3) 2.5 kV (4) 5 kv
ht, the​

Answer 1

Answer: use basic formula

Explanation:

Answer 2

Answer:

In an electron microscope, potential difference of  6.02Volt is needed to produce electrons of wavelength 5Å.

Therefore the option (2) is correct.

Explanation:

Given: wavelength of electrons $\lambda=5A=5*10^{-10}m$

Energy gained by electrons on applying voltage V:

Therefore, $E=eV$

We know, $\lambda=\frac{h}{\sqrt{2mE} } =\frac{h}{\sqrt{2m(eV)} }$

After squaring both sides we get,

$V=\frac{h^{2}}{2me\lambda^{2}}$                                                     ...................(1)

where $h=6.626*10^{-34}Js\\e=1.6*10^{-19}C\\m=9.1*10^{-31}kg$

Put all values in eq.(1),

$V=\frac{(6.626*10^{-34})^{2}}{2(9.1*10^{-31}kg)(1.6*10^{-19})(5*10^{-10})^{2}}$

$V=6.02Volt$