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Question:

De-Broglie wavelength of an electron accelerated by a voltage of 50 V is close to: (|e|=1.6×10⁻¹⁹C, me=9.1×10⁻³¹kg, h=6.6×10⁻³⁴Js)

0.5Å

1.7Å

2.4Å

1.2Å

Solution:

λ=h/p=h/√(2mE)=h/√(2mqV)
λ=6.6×10⁻³⁴/√(2×9.1×10⁻³¹×1.6×10⁻¹⁹×50)=1.72×10⁻¹⁰=1.72Å
Option B