In vacuum. The speed of light

Assertion (A): Sunlight reaches us without dispersion in the form of white light and not as its components. Reason (R): Dispersion takes place due to variation of refractive index for different wavelength but in vacuum the speed of light is independent of wavelength and hence vacuum is a non dispersive medium.

In vacuum speed of light depends upon

In vacuum, speed of light depends upon

In vacuum, speed of light depends upon

a) Speed of light is constant in vacuum. b) Speed of light depends on the wavelength of light when it passes through a medium. Which one is correct ? or both ?

If the speed of light in water is 2.25 xx 10^8 m/s Calculate the speed of light in vacuum .