**What is diffraction grating and obtain the grating equation to find the wavelength of light?**

Diffraction Grating is show of “A diffraction grating consists of a glass made plate on which excellent equidistant parallel lines (scratches) are drawn by mean of ruling engine with a fine diamond point. The transparent spacing between the scratches .on the glass plate ‘acts as slits”., Atypical diffraction grating has about 400 to 5000 lines per centimeter.

**Grating element:**

“The distance between the centers of two adjacent lines is called a grating element. ” Its value is obtained by dividing the length L Of the grating by the total number N of the lines ruled on it. So the grating element = d = L/N. If we consider the unit length of the diffraction grating then d = I/N.

**Working and Theory:**

Consider the parallel beam of monochromatic light illuminating the .grating at normal incidence the parts of the wavefront that. Pass through the slots behaves as a source of secondary wavelets according to Huygen’s principle. Consider the parallel rays which make an angle 0 with AB after diffraction. , They are then brought to focus on the screen at P by a convex lens. If the path difference between ray 1 and 2 is one wavelength I, they will reinforce each other at P. As the incident beam consists of the parallel rays, the rays from any two consecutive slits will differ in the path by A when they arrive at P. They will, therefore, interfere constructively.

**Grating Equation:**

The path difference for’ constructive interference between two consecutive rays should be an integral multiple of X, i.e., Path diff = ab = i. From is a right-angled triangle. Scholar’s PHYSICS —XI (Subjective) ab/ac = Sino ab = ac Sino ab = d sin O Comparing (1) and (2) X = d Sin According to equation if 0 00 , then path difference = O , so we will get a bright fringe.. This is known zero order image formed by the grating. If we increase O on either side, of this direction, a value of 0 will be arrived at which Sih O, and we again get a bright image. If the path ‘difference is the integral multiple of X, we will get second, third order, etc. images. Therefore, in general, we can write dsin0 = n), Where n = This is called the equation of granting and ‘n’ is called the Order of diffraction n = O, is the central maxima, n él is the first order maxima and so on. The separate images are obtained corresponding to each wavelength or color.

**Describe the diffraction of x-rays through crystals?**

Also, describe the Braggs equation and its different uses? Ans. Diffraction of X-Rays by Crystals X-rays is the type of electromagnetic radiation of much shorter wavelength, of the order of 10-10 m. To observe the effect of diffraction, the grating Spacing must be of the order of the wavelength of the radiation used. The regular array of atoms’in a crystal forms a natural diffraction grating. The stud/ of the atomic structure of crystals by X-rays was initiated in 1914 by W.H. Bragg and W.L Bragg with remarkable achievements.