CBSE Class 10 Physics The Human Eye and The Colourful World
Human Eye
Human eye works like a Camera.
Eye lens is a double convex lens.
Eye lens forms a real, inverted and smaller image of the object on the retina.
Power of the eye to observe distinctly the objects situated at widely different distances from the eye is called power of accommodation.
For normal human eye near point is 25 cm and far point is infinity.Defects of Vision
Myopia is defect of vision due to which a person is not able to see distant objects clearly and is corrected by using concave lens.
In Hypermertopia nearby objects are not clearly visible and is corrected by using convex lens.
Presbyopia is a defect due to weakening of ciliary muscles in old age and correct by using bi-focal lenses.Dispersion of Light
The phenomenon of splitting of white light into its constituent seven colours on passing through a glass prism is called dispersion of light.
Different colours undergo different deviations on passing through prism.
If a second identical prism is placed in an inverted position with respect to the first prism, all the seven colours recombine to form white light.
Rainbow is a natural spectrum appearing in the sky after a rain shower due to dispersion of light.Atmospheric Refraction
Atmospheric refraction is the phenomenon of bending of light on passing through earth's atmosphere.
As we move above the surface of earth, density of air goes on decreasing.
Light travelling from rarer to denser layers always bends towards the normal.
Stars twinkle on account of atmospheric refraction.
Sun appears to rise 2 minutes earlier and set 2 minutes later due to atmospheric refraction.Scattering of Light
The phenomenon in which a part of the light incident on a particle is redirected in different directions is called scattering of light.
Very small particles scatter lights of shorter wavelengths better than longer wavelengths.
The scattering of longer wavelengths of light increases as the size of the particles increases.
Larger particles scatter lights of all wavelengths equally well.
