VIVEKANANDHA ACADEMY

POWERPOINT PRESENTATION

THE HUMAN EYE AND THE COLOURFUL WORLD

CONTENT

•DISPERSION OF WHITELIGHT THROUG A PRISM•WHAT IS RAINBOW ?

What is Dispersion?

The splitting up of white light into its seven constituent colors on passing through a transparent medium (like glass prism) is called dispersion of light.

Cause of Dispersion

The dispersion of white light occurs because colors of white light travel at different speeds through the glass prism. The amount of refraction depends on the speed of colored light in glass. Now, since the different colors travel at different speeds, they are refracted by different angles on passing through the glass prism. So, when white light consisting of seven colors falls on a glass prism, each colour in it is refracted by a different angle, with a the result that seven colors spread out to form a spectrum.

Spectrum

The band of seven colors formed on a white screen, when a beam of white light is passed through a glass prism, is called spectrum of white light. The seven colors of the spectrum are: Violet, Indigo, Blue, Green, Yellow, Orange, and Red. It can be denoted by the word VIBGYOR.

Newton’s Experiment

Newton performed an experiment to show that white light consist of colors. A white light ray is passed through a prism to split it into the colors of the spectrum. The different colored light is allowed to pass through an identical prism kept in inverted position. The light emerging out of second prism was found to be white indicating that the light ray consist of colors.

Rainbow

A rainbow is a natural spectrum appearing in the sky after a rain shower. It is caused by dispersion of sunlight by tiny water droplets present in the atmosphere. A rainbow is always formed in a direction opposite to that of the Sun. The water droplets acts like a 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 colors reach the observer’s eye.

Lets Find Out More Facts

What is the range of visible light?

• Range of visible light – 0.4 microns to 0.7 microns.

• Visible light has a large number of radiations having wavelengths ranging from 0.4 microns to 0.7 microns. That is, red light has a large wavelength compared to violet light.

Which component deviates maximum?

• The violet colour has the minimum speed in prism, so the violet colour is deviated the maximum.

Which component deviates minimum?

• The red colour has the maximum speed in prism, so the red colour is deviated the minimum.

Rate of photosynthesis?

• Wavelength of the component that increases the rate of photosynthesis - 0.7 microns.

• The rate of photosynthesis is the most in the presence of red light.

Which colour doesn’t affect the rate of photosynthesis?

• Component which does not affect the rate of photosynthesis - green light.

• The rate of photosynthesis is zero in the presence of green light.

What is the nature of the spectrum emerging out of the first prism?

• Nature of the spectrum emerging out of the first prism - a band or spectrum of seven colors is obtained.

• The prism splits white light into seven colors.

What is the nature of the spectrum emerging out of the second prism?• Nature of the spectrum emerging out of the

second prism – white light is obtained.

• The seven colors of the visible spectrum combine to form white light.

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•DINESHWAREN.P•NISHOK.P.R• SETHURAM.S

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