Q.
An electron beam has a kinetic energy equal to 100eV. Find its wavelength associated with a beam, if mass of electron =9.1×10−31kg and 1eV=1.6×10−19J/eV. (Planck's constant =6.6×10−34Js)
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AIPMTAIPMT 1996Dual Nature of Radiation and Matter
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Solution:
Kinetic energy (E)=100eV;
Mass of electron (m)=9.1×10−31kg; 1eV=1.6×10−19J and
Planck's constant (h)=6.6×10−34J−s.
Energy of an electron (E)=100×(1.6×10−19)J
or λ=2mEh=2×9.1×10−31×100×1.6×10−196.6×10−34 =1.2×10−10m=1.2A˚