Question

Which of the following statements about fermions is false?

a) Photons are always fermions.

b) Electrons are always fermions.

c) Protons are always fermions.

d) Atomic nuclei are always fermions.

e) Lasers always depend on fermions.

Answer 1

Fermions are the odd spin half particle i.e. they have spin 1/2, 3/2, 5/2.....

Photons are NOT fermions as photons have spin 1.

Electrons and Protons are fermions as they have spin 1/2.

Atomic Nuclei can be bosonic or fermionic depends total spin of the constituent particles. Since nuclei contains protons or neutrons which are fermions but different number of these particles can give odd or even spin. As for Helium (He) nucleus there are 2 protons and 2 nutrons give total spin 2(1/2+1/2+1/2+1/2) so it is bosonic. While Lithium (Li) is fermionic as it has 3 protons and 4 neutrons.

Laser depends upon the number of photons in the cavity.

So (a) (d) and (e) are False.