Monochromatic light of wavelength 480 nm is incident from air on a glass surface. The refractive index of glass is 1.5. The ratio of the frequency of the incident light to that of the refracted light is .

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(4) 1:1. Given: λ = 480 nm in air, glass of refractive index 1.5. Idea: the frequency of light is fixed by the source. At the boundary the wave has to stay continuous, so exactly as many crests leave into the glass each second as arrive from the air. What the glass changes is the speed, v = c/n = (3×10⁸)/(1.5) = 2×10⁸ m/s, and with it the wavelength, λ' = λ/n = (480)/(1.5) = 320 nm. Check the frequency on both sides: (3×10⁸)/(480×10⁻⁹) = 6.25×10¹⁴ Hz and (2×10⁸)/(320×10⁻⁹) = 6.25×10¹⁴ Hz. They are equal, so the ratio of incident to refracted frequency is 1:1.

Monochromatic light of wavelength 480 nm is incident from air on a glass surface. The refractive index of glass is 1.5. The ratio of the frequency of the incident light to that of the refracted light is ______.

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