SATHEE: Modern Physics 7 Question 26

Modern Physics 7 Question 26

27. In an electron microscope, the resolution that can be achieved is of the order of wavelength of electrons used. To resolve a width of $7.5 \times 10^{- 12} m$ , the minimum electron energy required is close to

(Main 2019, 10 Jan I)

(a) $500 k e V$

(b) $1 k e V$

(d) $25 k e V$

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Solution:

Given, resolution achieved in electron microscope is of the order of wavelength.

So, to resolve $7.5 \times 10^{- 12} m$ seperation wavelength associated with electrons is

$λ = 7.5 \times 10^{- 12} m$

$∴$ Momentum of electrons required is

$p = \frac{h}{λ}$

or kinetic energy of electron must be

$K E = \frac{p^{2}}{2 m} = \frac{(h / λ)^{2}}{2 m}$

Substituting the given values, we get

$\begin{aligned} = \frac{\frac{6.6 \times 10^{- 34}}{7.5 \times 10^{- 12}}}{2 \times 9.1 \times 10^{- 31}} J \\ = \frac{{(6.6 \times 10^{- 34})}^{2}}{2 \times 9.1 \times 10^{- 31} \times {(7.5 \times 10^{- 12})}^{2} \times (1.6 \times 10^{- 19})} e V \\ (∵ 1 e V = 1.6 \times 10^{- 19} J) \\ = 26593.4 ≃ 26.6 \times 10^{3} e V ≃ 26 k e V \end{aligned}$

which is nearest to $25 k e V$ .

Modern Physics 7 Question 26

27. In an electron microscope, the resolution that can be achieved is of the order of wavelength of electrons used. To resolve a width of $7.5 \times 10^{- 12} m$ , the minimum electron energy required is close to

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Modern Physics 7 Question 26

27. In an electron microscope, the resolution that can be achieved is of the order of wavelength of electrons used. To resolve a width of 7.5×10−12m, the minimum electron energy required is close to

Solution:

Engineering Preparation

Medical Preparation

NCERT Books & Solutions

Important Resources

Other Resources

Syllabus

Test Platform

Sample Mock Test

Mentorship

NCERT Exercise Video Solution

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27. In an electron microscope, the resolution that can be achieved is of the order of wavelength of electrons used. To resolve a width of $7.5 \times 10^{- 12} m$ , the minimum electron energy required is close to