Answer :
By uncertainty principle
λ = h / p.
Where λ = wavelength, h = Planck's constant = 6.63 * 10⁻³⁴ Js
λ = wavelength = 550 nm = 550 * 10⁻⁹ m, Mass of electron = 9.1 * 10 ⁻³¹ kg
p = Momentum = mv
λ = h / mv
v = h / mλ
v = 6.63 * 10⁻³⁴ / (9.1 * 10⁻³¹ * 550 * 10⁻⁹)
v = 1 324 675.325 m/s
v ≈ 1.325 *10⁶ m/s
λ = h / p.
Where λ = wavelength, h = Planck's constant = 6.63 * 10⁻³⁴ Js
λ = wavelength = 550 nm = 550 * 10⁻⁹ m, Mass of electron = 9.1 * 10 ⁻³¹ kg
p = Momentum = mv
λ = h / mv
v = h / mλ
v = 6.63 * 10⁻³⁴ / (9.1 * 10⁻³¹ * 550 * 10⁻⁹)
v = 1 324 675.325 m/s
v ≈ 1.325 *10⁶ m/s