What voltage must be applied to an elect-non microscope to produce electrons of wavelength `0.4A`?

Explanation

To solve the problem of finding the voltage that must be applied to an electron microscope to produce electrons of wavelength \(0.4 \, \text{Å}\), we can follow these steps:

### Step 1: Understand the relationship between wavelength and voltage
The wavelength of an electron can be related to the voltage applied using the de Broglie wavelength formula:
\[ \lambda = \frac{h}{\sqrt{2m eV}} \]
where:
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