The wavelength of electrons accelerated from rest through a potential difference of 40 kV is X × 10 - 12   m . The value of x is. (Nearest integer) Given: Mass of electron = 9 . 1 × 10 - 31   kg Charge on an electron = 1 . 6 × 10 - 19 C Planck's constant = 6 . 63 × 10 - 34 Js

Step-by-step solution

De-broglie-wave length of electron: λ e = h 2   m ( KE ) ∵ e - is accelerated   from rest  ⇒ KE = q × V λ = h 2 mqv = 6 . 63 × 10 - 34 2 × 1 . 6 × 10 - 19 × 9 . 1 × 10 - 31 × 40 × 10 3 = 0 . 614 × 10 - 11   m = 6 . 14 × 10 - 12   m Nearest integer = 6 OR λ = 12 . 3 V Å = 12 . 3 200 = 6 . 15 × 10 - 12   m Ans. is 6