Test: Dispersion of Light - UPSC

Red light has a longer wavelength than violet light.The refractive index of red light in glass is 1.513.

The sun probably does have some albedo, but there's no light for it to reflect. At least, not significant amounts. The only incident light on the sun comes from the stars, and there's very, very little of that, as you can tell from walking out on a moonless night.

Re - combination of seven colours is done with the help of two inverted prisms.

When white light falls on a glass prism, each colour in it is refracted by a different angle, from which red colour is least deviated and violet most.

When the light travels through the glass, different spectrums of light travel through at different speeds. Spectrums with short wavelengths get slowed down much more than those with longer wavelengths. When light is slowed as it enters a medium it is refracted. That is, it changes direction. The more it's slowed, the further towards the “normal line” it will go. So slower light will bend more than faster light. The differences in speed that each spectrum of light has as it passes through the medium causes different angles of refraction, which in turn causes dispersion. As the light leaves the prism it disperses even more due to the light speeding up again. Because each spectrum travels at different speeds while in the glass they don't reach the other side at the same time. So, the red spectrum exits first and speeds up first while the blue or violet spectrum exits last and speeds up last.

Angle of deviation is the deviation of moving objects which can be ray of light or solid object from its path after refraction or reflection. It measures how much something deviate from its path after it meets obstacles in its path.

Black is the absence of all light. Things appear black when they do not reflect or emit light. White is the presence of all colors of visible light. Objects appear white when they reflect or emit all wavelengths of visible light (or at least three wavelengths - Red, Blue and Green - in equal intensity.

A rainbow is formed when light (generally sunlight) passes through water droplets hanging in the atmosphere. When light reflects off a water droplet, it simply bounces back in the opposite direction from where it originated. When light refracts, it takes a different direction.

The phenomena due to which white light splits Into seven colours on passing through a prism is called dispersion. Upon passing through a medium, each of the colors travels at different speeds and hence has different angles of refraction leading to the splitting of the light.