If the momentum of an electron is required to be the same as that of a photon of wavelength 5200 A, its velocity should be m s⁻¹.

Question

Accepted Answer

(2) 1.4×10³. Given: λ = 5200 A = 5.2×10⁻⁷ m; take h = 6.63×10⁻³⁴ J s and electron mass m = 9.1×10⁻³¹ kg. Idea: a photon of wavelength λ has momentum p = h/λ; the electron needs mv = p. p = (6.63×10⁻³⁴)/(5.2×10⁻⁷) = 1.275×10⁻²⁷ kg m s⁻¹ v = p/m = (1.275×10⁻²⁷)/(9.1×10⁻³¹) = 1.40×10³ m s⁻¹ So the electron must move at about 1.4×10³ m s⁻¹.

If the momentum of an electron is required to be the same as that of a photon of wavelength 5200 A, its velocity should be ______ m s⁻¹.

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