DISPERSION OF LIGHT,RAINBOW

                              DISPERSION OF LIGHT

COMPOSITE LIGHT

Any light composed of two or more colours is called a composite light

DISPERSION OF LIGHT

Splitting up of a composite light in to its component colours is called Dispersion of light

NEWTON'S EXPERIMENT

 Allow sunlight (To make a narrow beam of light use a mirror and slit)  to fall obliquely on the face of a triangular glass prism.

On the other side we can observe seven colours.Violet colour seems near the base of prism.ie violet deviates more and Red deviate less. From this we can conclude sunlight consist if seven colours. So it is a composite light.

What are the colours formed on the wall?

Violet, Indigo, Blue,Green, Yellow ,Orange ,Red (VIBGYOR). The orderly arrangement of these colours is called Spectrum

Colour                     wave length(nm)

Violet                        400-440

Indigo                       440-460

Blue                          460-500

green                         500-570

yellow                        570-590

orange                       590-620

red                             620-700 

Is there any connection between wavelength and deviation of constituent colours?explain

Yes, When composite light enter from air to prism(glass) there refraction take place.When light emerge out to air from glass there is another refraction take place .According to change in wave length refraction take place at different rates.. According to the difference in wavelength the rate of deviation varies in each colour. The colour with lowest wavelength deviates most. The colour with highest wavelength deviates less. 

Why the light of torch, candle appears yellow instead of white, even though it contain same spectrum of sunlight?

 The intensity of blue color is less in the light of candle and torch . So it appears in yellow. 

CAN WE RECOMBINE THE DISPERSED COLOURS IN THE WHITE LIGHT?

Yes, Arrange the two prisms as shown in figure

                                 RAINBOW

The sunlight that incident at a suitable angle at the top of a water drop undergo two refraction and one total internal reflection inside the water drop. So the white light split in to its constituent colors.

 Why Rainbow appears in Arc Shape?
The line joining the centre of the rainbow and the observsr is called line of vision.Each color of the dispersed sun light  make a definite angle with the line of vision.For an observer from earth can see only one color from a single drop. All water drops appearing in the same colour make the same angle with line of vision.