Question

The wavelengths for the light of red and blue colours are roughly $7.8\times {10}^{-7}m$ and $4.8\times {10}^{-7}m$ respectively. Which colour has the greater speed in glass?

• A. Red light
• B. Violet light
• C. Yellow light
• D. All colors have same speed

Answer 1

The correct option is A Red light

When travelling through a medium, the frequency of light doesn't change. Hence, red light having the maximum wavelength will travel fastest through glass as speed of light is given by $v=f\lambda$ where; $f$ is the frequency and $\lambda$ is the wavelength of light travelling at speed $v$.