A particle of mass 1mg has the same wavelength as an electron moving with a velocity of 3 x 10⁶ ms⁻¹. The velocity of the particle is: (mass of electron = 9.1 x 10⁻³¹ kg)

Options

(a) 2.7 x 10⁻¹⁸ ms⁻¹
(b) 9 x 10⁻² ms⁻¹
(c) 3 x 10⁻³¹ ms⁻¹
(d) 2.7 x 10⁻²¹ ms⁻¹

Correct Answer:

2.7 x 10⁻²¹ ms⁻¹

Explanation:

Wavelength of particle (λ₁)
= h/mv = h / (1 x 10⁻³) x v
where v is the velocity of the particle. Wavelength of electron
(λ₂) = h / (9.1 x 10⁻³¹) x (3 x 10⁶)
But λ₁ = λ₂
h / (1 x 10⁻³) x v = h / (9.1 x 10⁻³¹) x (3 x 10⁶)
v = (9.1 x 10⁻³¹) x (3 x 10⁶) / 10⁻³
= 2.7 x 10⁻²¹ ms⁻¹