If two slits have width ratio 1 : 4. The ratio of maximum to minimum intensities in the interference pattern would be.

9 : 1

The correct answer is Option (3) → 9 : 1

The maximum intensity occurs when the waves are in phase.

$I_{max}∝(A_1+A_2)^2=(1+2)^2=9$

$I_{min}∝(A_1-A_2)^2=(1-2)^2=1$

Minimum intensity occurs when the waves are out of phase.

$∴\frac{I_{max}}{I_{min}}=\frac{9}{1}$