Calculate the maximum number of possible interference . . .

Question : Calculate the maximum number of possible interference maxima for the slit separation qual to twice the wavelength in Young's double slit expertment.

Doubt by Ridhi 

Solution : 
d = 2λ
We know, in interference
θ≈nλ/d
or
sinθ=nλ/d
sinθ=nλ/2λ
sinθ=n/2
2sinθ=n
n=2
sinθ
The  value of sin
θ fluctuate between -1 and 1 (both included)

So, possible value of n would be 2(-1) to 2(+1)
or 
-2 to +2 
i.e. -2, -1, 0, 1 and 2.

Hence, the maxium number of possible maxima would be 5.