Question

a glass prism is immersed in water what happens to the value of angle of minimum deviation​

Answer 1

The angle of minimum deviation is attained when the angle of incidence and angle of emergence for a ray of light being refracted through a prism, are equal. The angle of minimum deviation depends on the refractive index of the medium through which the light passes.

Since the refractive index of prism glass which is submerged in water is less than the refractive index of the prism in air, there will be a decrease in the angle of minimum deviation