What is diffraction grating? What is the advantage of increasing the number of lines in the grating?
1.A diffraction grating is an arrangement consisting of a large number of parallel slits of same width and separated by equal opaque spaces.
2.It is obtained by ruling equidistant parallel lines on a glass plate with the help of a diamond.
3.The lines act as opaque spaces and the incident light cannot pass through them.The space between the two lines is transparent to light and acts as a slit.
4.The spacing between the lines is of the order of wavelength of visible light.The number of a lines in a plane transmission grating is of the order of 15000 to 20000 per inch.
Advantage of increasing the number of lines in the grating are :
(a)The number of principal maxima that can be seen on a screen increases.
(b)The distance between two adjacent principal maxima increases.