Answer & explanation
Correct answer: option 1
$\text{Distance between first maxima and fifth minima is } \frac{7\lambda D}{2d}$
$\Rightarrow \frac{7\lambda D}{2d} = 7mm$
$\Rightarrow \lambda = 600nm$
Correct answer: option 1
$\text{Distance between first maxima and fifth minima is } \frac{7\lambda D}{2d}$
$\Rightarrow \frac{7\lambda D}{2d} = 7mm$
$\Rightarrow \lambda = 600nm$