If red, blue, green and yellow lights are allowed to enter the same glass block with the same angle of incidence (∠i), then for which colour will the angle of…

blue

Reason — The refractive index of a given transparent medium decreases with the increase in the wavelength of light. Among red, yellow, green and blue, blue light has the shortest wavelength, so glass has the highest refractive index for blue light.

Since a medium of higher refractive index bends the light more, blue light is refracted (i.e., deviated) the most and red light the least for the same angle of incidence.

Hence, the angle of deviation is greatest for blue light.