Question
An electron of mass m and a photon have the same energy E. The ratio of de-Broglie wavelength associated with them is,
Solution
D.
Given that electron has a mass m.
De-Broglie wavelength for an electron will be given as,
where,
h is the Planck's constant, and
p is the linear momentum of electron
Kinetic energy of electron is given by, E = 
From equation (i) and (ii), we have
Energy of a photon can be given as,
Hence, 
is the de-Broglie wavelength of photon.
Now, dividing equation (iii) by (iv), we get
