Uncertainty relation between number of photons in an EM field and its phase

[Myrddin]

Derive the relation Δn.Δσ ≥ 1/2

where n is number of photons in an EM field and σ is phase

Using heisenburgs uncetertainty principle?

Tried subbing in frequency into heisenburgs uncertainty principle to get to the number of photons and to get rid of mometum is this the right line? Dont know about getting the phase term?

 

[Azelketh]

$$\Delta E = hf \Delta n$$

and something to do with $$E=E0 \exp( i(\omega t - kx +\psi ))$$ where $$\psi = phase$$