Tyndall Scattering When a beam of sunlight, enters into a dusty room through a window, then its path becomes visible to us. This is because, the tiny dust particles present in the air of the room scatter the beam of light. This is an example of Tyndall Scattering The scattering of light rays by the colloidal particles in the colloidal solution is called Tyndall Scattering or Tyndall Effect. Do you Know Colloid is a microscopically small substance that is equally dispersed throughout another material.
Example: Milk, Ice cream, muddy water, smoke Raman scattering When a parallel beam of monochromatic (single coloured ) light passes through a gas or liquid or transparent solid, a part of light rays are scattered. The scattered light contains some additional frequencies (or wavelengths) other than that of incident frequency (or wavelength). This is known as Raman scattering or Raman Effect. Raman Scattering is defined as “The interaction of light ray with the particles of pure liquids or transparent solids, which leads to a change in wavelength or frequency.” The spectral lines having frequency equal to the incident ray frequency is called ‘Rayleigh line’ and the spectral lines which are having frequencies other than the incident ray frequency are called ‘Raman lines’.
The lines having frequencies lower than the incident frequency is called stokes lines and the lines having frequencies higher than the incident frequency are called Antistokes lines. You will study more about Raman Effect in higher classes. . LENSES A lens is an optically transparent medium bounded by two spherical refracting surfaces or one plane and one spherical surface.
Lens is basically classified into two types. They are: (i) Convex Lens (ii) Concave Lens (i) Convex or bi-convex lens: It is a lens bounded by two spherical surfaces such that it is thicker at the centre than at the edges. A beam of light passing through it, is converged to a point. So, a convex lens is also called as converging lens.
(ii) Concave or bi-concave Lens: It is a lens bounded by two spherical surfaces such that it is thinner at the centre