Question

Two parallel rays of red and violet travelling through air meet the air-glass boundary as shown in the diagram. Will their paths inside the glass be parallel? Give a reason for your answer. Compare the speeds of the two rays inside the glass.

Answer 1

No, their paths inside the glass will not be parallel.

Reason: Glass has a different refractive index for different colours of light. The refractive index of glass for violet light is greater than that for red light (μ_v > μ_R). Therefore, the violet ray will bend (deviate) more towards the normal than the red ray inside the glass, causing their paths to diverge and no longer remain parallel.

Comparison of Speeds: The speed of red light inside the glass is greater than the speed of violet light `(v_"red" > v_"violet")`.