Ray optics

In media like glass, different wavelengths in the electromagnetic spectrum travel at different speeds. Refractive index (μ) is related to wavelength (λ) of light as μ=A+B/lambda^2 Again μ = Speed of light in Vaccum/Speed of light in medium Hence, speed of light in media is proportional to wavelength... Since wavelength increases from Violet to Red, Red travels the fastest.

Correct answer (a) red lights travels faster than other colours because as wavelength increases speed also increases