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 .