Question

The wavelength of a moving electron having 4.55 × 10⁻²⁵ J of
kinetic energy is :
(a) 7.27 × 10⁻⁷ metre (b) 72.7 × 10⁻⁷ metre
(c) 7.27 × 10⁻⁹ metre (d) 72.7 × 10⁻⁹ metre

Answer 1

answer : option (a) 7.27 × 10^-7 metre.

kinetic energy of a moving electron, K.E = 4.55 × 10⁻²⁵ J

using De - Broglie's wavelength equation,

λ = h/√(2m.K.E)

where m = 9.1 × 10^-31 kg

h = 6.625 × 10^-34 J.s

now λ = 6.625 × 10^-34/√{2 × 9.1 × 10^-31 × 4.55 × 10^-25)

= 6.625 × 10^-34/√(9.1 × 9.1 × 10^-56)

= 6.625 × 10^-34/9.1 × 10^-28

= (6.625/9.1) × 10^-6

= 0.728 × 10^-6

= 7.28 × 10^-7 metre.

hence option (a) is correct choice.

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