Issac Newton: He was the first, who obtained spectrum of sunlight by using glass prism. He tried to split the spectrum of white light more by using another similar prism, but he could not get any more colours.

Opticaldispersion

Formation of the rainbow: The water droplets act like small prism. They refract and disperse the incident sunlight, then reflect it internally, and finally refract it again when it comes out of the raindrop. Due to the dispersion of light and internal reflection, different colours reach the observer’s eye.Red colour appears on top and violet at the bottom of rainbow.A rainbow is always formed in a direction opposite to that of Sun.

Rainbow: It is the spectrum of sunlight in nature. It is formed due to the dispersion of sunlight by the tiny water droplet, present in the atmosphere.

Dispersion

Dispersion is the basis for the prism and its ability to separate light according to wavelength. When a light ray passes through a prism it splits up in to its constituent colors producing spectrum of seven colors namely violet, indigo, blue, green, yellow, orange, red. This phenomenon of splitting up of light in two constituent colors is called dispersion. Dispersion is the basis for the prism and its ability to spatially separate light according to wavelength, as illustrated in the following animation.

BESANTEK Digital Light Meter used to measure the amount of light. It is used in the general field of lighting, where it can help to reduce the amount of waste light used in the home, light pollution outdoors and plant growing to ensure proper light levels.

Refractionby prism

The most common dispersion is a rainbow. Sunlight falls on a falling raindrop, the ray is refracted into the drop, and some of the light reflects off the inner surface of the drop and then refracts outward. The first refraction causes the light to split into a spectrum. The second quarry enlarges. Light is refracted in large numbers. Red comes from dropsabove and purple below. If the Sun is higher above the horizon, the rainbow cannot be seen.

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Newton found that when an inverted prism is placed in the path of dispersed light then after passing through the prism, they recombine to form white light.

Opticalprism

He repeated the experiment using second prism in inverted position with respect to the first prism. It allowed all the colours of spectrum to pass through second prism. He found white light emerges on the other side of second prism.