Answer:
[tex]\lambda = 424.4 nm[/tex]
Explanation:
As we know by the formula of diffraction
[tex]a sin\theta = N\lambda[/tex]
so we have
a = slit size
[tex]\theta [/tex] = angular position of Nth minimum
so we will have
for first minimum of 630 nm light
[tex]a sin40 = 1(630 \times 10^{-9})[/tex]
[tex]a = 9.8 \times 10^{-7} m[/tex]
Now for another wavelength second minimum is at 60 degree angle
[tex]a sin60 = 2 \lambda[/tex]
[tex](9.8 \times 10^{-7}) sin60 = 2 \lambda[/tex]
[tex]\lambda = 424.4 nm[/tex]