The 630 nm light from a helium neon laser irradiates a grating. the light then falls on a screen where the first bright spot is separated from the central maxim by 0.51m. light of another wavelength produces its first bright spot at 0.39 m from its central maximum. determine the second wavelength.

The second wavelength is 482 nm.

Explanation:

Given that,

Wavelength = 630 nm

Distance from central maxim = 0.51 m

Distance from central maxim of another wavelength = 0.39 m

We need to calculate the second wavelength

Using formula of width of fringe

Here, d and D will be same for both wavelengths

= wavelength

= width of fringe

The width of fringe for first wavelength

....(I)

The width of fringe for second wavelength

....(II)

Divided equation (I) by equation (II)

Hence, The second wavelength is 482 nm.

real, smaller and upside-down.   so the answer should be b.