While light has so many wavelengths why only 3 colours exist as primary colours? Why do some colours disperse while VIBGYOR colours don't (except the primary ones which satisfy the logic as they are basic colours)
Red, green and blue are called primary colors because when mixed they give us an impression of what we call white light, where "white" means the impression produced in our brain by a range of frequencies as emitted by a black body at a certain temperature, about 6000K, the temperature of the sun surface. In the classic experiment, a spinning disc has three sectors painted RGB but the color appears white. We use the same concept for "white" noise - a continuous range of frequencies, not single frequencies.