Consider the de Broglie wavelength of an electron and a proton. Which wavelength is smaller if the two particles have (a) the same speed (b) the same momentum (c) the same energy?
De Broglie wavelength is given by
Where 
=Planck’s constant; 
=mass of the particle; 
=momentum and 
=velocity of the particle
Mass of electron 
kg; mass of proton 
kg
(a) Electron and Proton both have same speed
The wavelength of proton is smaller than that of electron.
(b) Electron and Proton both have same momentum
The wavelength of proton is equal to that of electron.
(c) Electron and Proton have same energy
De Broglie Wavelength is also given by
Where 
=Energy of the particle
The wavelength of proton is smaller than that of electron.
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