Diffraction Grating

INTRODUCTION

Usually light is thought to have always traveling in straight parallel lines, but when light waves pass around the edge of an object they tend to bend around that edge and become spread out. Diffraction of light occurs when a light wave passes by a corner or through an opening or slit that is physically the approximate size of, or even smaller than that of the said light's wavelength.

White light is light that is made up of a combination of light with frequencies in the red, orange, yellow, green, blue, indigo and violet parts of the spectrum.

Young's double-slit experiment is an experiment conducted to show how light behaves as a wave and as well as a particle. Usually we tend to think light travels in a straight line unhindered but in reality its quite different. When passed through a double slit it shows constructive and destructive interference hence proving that light has wave-like properties as shown below

Diagram showing young’s double slit experiment

In the diagram above , where its marked ‘B’ on the screen indicates constructive interference via bright fringes and where its marked ‘D’ on the screen indicates destructive interference via darker shaded fringes of light.

A diffraction grating consists of a number of closely spaced slits. The slits are so small they are not visible to the naked eye. Light passing through a diffraction grating will produce an observable interference pattern.

Huygens’ Principle is based on the assumptions that each point on the primary wavefront acts as a source of secondary wavelets, sending out disturbance in all directions in a similar manner as the original source of light does. The new position of the wavefront at any instant (called secondary wave front) is the envelope of the secondary wavelets at that instant as shown in the diagram below.

Diagram showing Huygen’s Principle