Two large parallel plates are connected with the terminal of `100 V` power supply. These plates have a fine hole at the centre . An electron having energy `200 eV` is so directed that it passes through the holes . When it comes out its de - Broglie wavelength is

Options

A. `1.22 Å`
B. `1.75 Å`
C. `2 Å`
D. None of these

Answer

A

Explanation

Energy of the electron , when it comes out from the second plate ` = 200 eV - 100 eV = 100 eV`
Hence accelerating potential difference ` = 100 V`
`lambda_(el ectron) = (12.27)/(sqrt(V)) = (12.27)/(sqrt(100)) = 1.23 Å`