Question

which colour has the greatest speed in the visible region??and why???

Answer 1

The index of refraction through a glass (say, a prism) is 1.514 for red light/colour, under the prevalence of a normally dispersive medium, due to its lowest frequency and longest wavelength (among the seven colours of VIBGYOR)

These conditions support the fact that red colour has the greatest speed in the visible region.

Answer 2

Answer:

Since red has a larger wavelength, it has a smaller refractive index. This means that red has the largest speed in the visible spectrum and violet the lowest.

Explanation:

All the EM waves have the same speed in vacuum, that is, the speed of light c. That means it doesn't matter what color you light is, it will travel with the speed of light, in vacuum of course.

Except for when the light is in a different medium, say a prism, then it is a function of the refractive index of the light. Refravtive index is inversely proportional to the wavelength of the light. Red has the largest wavelength in the visible spectrum. Conversely, Violet has the smallest.

Now,

Refractive index=speed in vacuum/speed in medium.

Since red has a larger wavelength, it has a smaller refractive index.

This means that red has the largest speed in the visible spectrum and violet the lowest..

Light, having any wavelength or frequency, being an electromagnetic wave, will always travel at the speed of light (3×10^8) m/s. Now the fact that people think the speed changes in different mediums is not true. When a beam of light, say in air travelling at its speed, enters a denser medium, say glass, every photon has to pass through the atoms and molecules of the constituents of medium, so every photon gets absorbed and re-emitted by the atom and this process takes time, hence we feel that the speed of light decreases in the medium.

These photons are massless packets or quanta of energy that only travel at the speed of light, not less not more.

Hence in this process the low frequency light, say red, will disperse more, hence more number of collisions, so will take more time to pass through.

The index of refraction through a glass (say, a prism) is 1.514 for red light/colour, under the prevalence of a normally dispersive medium, due to its lowest frequency and longest wavelength (among the seven colours of VIBGYOR)

These conditions support the fact that red colour has the greatest speed in the visible region