What is the wavelength in nm of a light whose first order bright band forms a
diffraction angle of 30 degrees, and the diffraction grating has 700 lines per
mm? (give answer in whole number format) *

The wavelength of the first order bright band light light is 714 nm .

Explanation:

We have to find the wavelength of the first order brightness of a light. Here we are using Huygen's principle of light.

The formula is

nλ =d sinθ

where, n is the order of maximum

            λ is the wavelength of light

            d is the distance between the lines on diffraction grating.

            θ is the angle.

For the given equation n is 1 because the problem states that the light forms 1st order bright band

  λ  is unknown.

d = or 0.0000014 m

sin (30) = 0.5

so,

1(λ) = (0.0000014)(0.5)

     = 0.0000000714

     = 714 nm

Thus, The wavelength of the first order bright band light light is 714 nm .

it may be wrong but i think its a