Narrow, bright fringes are observed on a screen behind a diffraction grating. The entire experiment is then immersed in water. Do the fringes on the screen get closer together, get farther apart, remain the same, or disappear? Explain.

 n (a sin θ) =  m λ₀

n> 1, therefore the fringes move away from each other

Explanation:

The diffraction experiment the constructive interference fringes is described by

          a sin θ = m λ₀

in this equation it is assumed that the experiment emptied the air n = 1

When the same experiment is performed in water, the wavelength changes

           λₙ = λ₀ / n

execution for constructive interference

            a sin θ = m λₙ

we substitute

           a sin θ = m λ / n

           n (a sin θ) =  m λ₀

the refractive index of water is n = 1.33, so for the same wavelength the separation of the spectrum is multiplied by n> 1, therefore the fringes move away from each other

hypothesising or postulating

layers of the earth affect the waves and these effects are seen on instruiments such as seimometers