A beam of monochromatic light is refracted from vacuum into a medium of refractive index 1.5, the wavelength of refracted light will be

From  μ=cv=nλvnλm,λm=λvμHere, c = velocity of light in medium andV = velocity of light in vacuum; m = refractive index of the medium.Hence, wavelength in medium  λm<λa∵μ>1,givenSo, the required wavelength decreases.Alternatively,v=fλ , On refraction, the frequency, f do not change. When light is refracted from vacuum to a medium, the velocity, v decreases. Therefore, λ  also decreases.