Question

Which colour of white light travels slowest, in glass?

• A. Blue
• B. Violet
• C. Red
• D. Yellow

Answer 1

The correct option is B Violet

The velocity of light is given by v= $f\lambda$ where $f$ is the frequency and $\lambda$ is the wavelength.
When travelling through a medium the frequency remains unchanged and hence, speed depends upon the wavelength of light. Violet light having the least wavelength travels slowest.