The wavelengths for the light of red and blue colours are distinctly different. In this context, consider the following statements:

In vacuum, both red and blue colours have same speed

In glass, the speed of red colour is more than blue colour

Which among the above statements is / are correct?

Question

In vacuum, both red and blue colours have same speed. This statement is CORRECT. In vacuum, all electromagnetic waves travel at the same speed, which is the speed of light (c = 3x108 m/s). This is true regardless of wavelength or color.
In glass, the speed of red colour is more than blue colour. This is CORRECT. In glass, the refractive index depends on wavelength - it is higher for shorter wavelengths like blue. Since speed is inversely related to refractive index, the speed of red light (longer wavelength) will be more than the speed of blue light. So in glass, red light does travel faster than blue light.

GKToday Admin · Accepted Answer

Both 1 & 2 are correct

In vacuum, both red and blue colours have same speed. This statement is CORRECT. In vacuum, all electromagnetic waves travel at the same speed, which is the speed of light (c = 3x108 m/s). This is true regardless of wavelength or color.
In glass, the speed of red colour is more than blue colour. This is CORRECT. In glass, the refractive index depends on wavelength - it is higher for shorter wavelengths like blue. Since speed is inversely related to refractive index, the speed of red light (longer wavelength) will be more than the speed of blue light. So in glass, red light does travel faster than blue light.

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