Question

An electron accelerated by a p.d of V possess a de-Broglie wavelength λ. If the accelerating potential is increased by a factor 4. The de-Broglie wavelength of the electron will 

(1) remain unchanged 

(2) becomes 4 times

(3) become double 

(4) become halved

Answer 1

Correct option : (4) become halved

Explanation : 

When an electron is accelerated through a potential V its energy becomes eV and hence 1/2 mv² = eV

Hence whenever V is increased by a factor of 4 λ will get halved.