For a wavelength of 420 nm, a diffraction grating produces a bright fringe at an angle of 24°. for an unknown wavelength, the same grating produces a bright fringe at an angle of 39°. in both cases the bright fringes are of the same order m. what is the unknown wavelength?

649.8420 nm

Explanation:

We have given

we have to find unknown wavelength that is

The condition for constructive interference is

Where d is distance between slits is angle of emergence and n is order of maxima

Using constructive interference equation

---------eqn 1

---------eqn 2

On dividing eqn 1 by eqn 2

this allows people to make the best decision or pursue the best option. when alternatives are weighed using their advantages and disadvantages, the option whose disadvantages outweigh the advantages (based on a qualitative or quantitative analysis) are shunned while those whose advantages outweigh their disadvantages are pursued.