Question

What is momentum speed and de broglie wavelength of an electron with kinetic energy of 129 ev?

Answer 1

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Answer 2

Given

Kinetic energy of electron = 129 eV

We know mass of an electron m = 9.1× 10⁻³¹ kg

We have momentum of an electron p = √(2mE)

Thus

p =√(2×9.1×10⁻³¹×129×1.6×10⁻¹⁹) = 62.9×10⁻²⁴

Now we know momentum p is expressed mathematically as

p = m v

v = p/m = 62.9×10⁻²⁴/9.1× 10⁻³¹

v = 6.92×10⁷

Now solving for Debrogile wavelength

λ = h/p ; here h = plank's constant = 6.63×10⁻³⁴

λ = 6.63×10⁻³⁴/62.9×10⁻²⁴= 0.105 ×10⁻¹⁰