Rayleigh scattering can be considered to be elastic scattering since the photon energies of the scattered photons are not changed.

Diffraction is the slight bending of light as it passes around the edge of an object. The amount of bending depends on the relative size of the wavelength of light to the size of the opening.

Based on Rayleigh scattering, the Rayleigh criterion for the diffraction limit is used to define the resolution. It states that two images which are just resolvable when the centre of the diffraction pattern of one is directly over the first minimum of the diffraction pattern of the other.

What isobjective lensinmicroscope

The resolving power of a microscope is the ability of the microscope to show as separate images of two-point objects lying close to each other.

Low powerobjective microscope function

Where λ is the wavelength of the light, n is an integer value, a is slit width and D is the distance of the screen from the slit.

The Rayleigh criterion specifies the minimum separation between two light sources that may be resolved into distinct objects.

High powerobjective microscope function

The slits are separated by opaque spaces. When a wavefront is an incident on a grating surface, light is transmitted through the slits and obstructed by the opaque portions. Such a grating is called transmission grating.

Now if d is the separation between two slits, N is the number of diffractions grating and θ is some angle for the first maxima then the angular width can be expressed as

In Young’s double-slit experiment, an interference pattern comprising alternate dark and bright fringes on-screen was observed. However, in that experiment, we have assumed each slit as behaving like a point source thus we did not consider the width of the slit, as a result, no diffraction pattern was observed due to either slit.

The resolving power of a diffraction grating is defined as its ability to form separate diffraction maxima of two closely separated wavelengths.

Objective lensmagnification

Function ofcondenser inmicroscope

Francesco Grimaldi made the first observation of diffraction in 1665. When light waves were forced to pass through a slit, he observed that they dispersed. Later, it was discovered that diffraction happens everywhere light waves bend around a corner, not just in tiny slits or holes.

The capacity of an optical instrument to show separate images of very closely placed two objects is called resolving power.

A distinctive element of the diffraction pattern is the centre maxima, also referred to as the central fringe. A distinctive element of the diffraction pattern is the centre maxima, also referred to as the central fringe. The secondary minima and maxima, which encircle the centre maxima, are made up of dark and bright lines.

Now if the width of each slit is finite, we shall observe a combined effect of diffraction (through each slit) as well as interference pattern as we can see in the figure below.

Typesof objectivelenses

The most common example of diffraction occurs with water waves that bend around a fixed object. Light bends similarly around the edge of an object.

The reciprocal of the smallest angle subtended at the objective lens of a telescope by two-point objects which can be just distinguished as separate is called the resolving power of a telescope.

Now at any point on the screen, the rays reaching from the first and second slit will have a path difference, where ‘b’ is the separation between the center of two slits.

Microscopeparts

Function ofstage inmicroscope

A diffraction grating is an extremely useful device, and one of it consists of a large number of narrow slits side by side.

We hope that the above Physics Optics detailed notes helped you to understand the importance of the Diffraction of Light. Do practice it now on the Testbook App through the free mock tests.

Atmosphere consists of many different particles and molecules of gases and dirt, suspended or in relative motion. When sunlight passes through the atmosphere, it hits these particles and gets diffracted. This diffraction also scatters light. For example, Light can enter the room through a small hole, get diffracted and fill the room.

Although light is typically thought to move in straight lines, when it comes close to a barrier, it tends to bend around the barrier and disperse out. The dispersion of waves as they go through or around a barrier is referred to as diffraction. Diffraction of light, more precisely, happens when a light wave passes by a corner or through an opening or slit that is physically as tiny as, or even smaller than, that light’s wavelength.

As explained above Diffraction of light is the phenomenon of bending light from the sharp corners of a slit or obstacle and spreading into the region of the geometrical shadow.

where, λ is the wavelength of light (or other electromagnetic radiation) and D is the diameter of the aperture, lens, mirror, etc., with which the two objects are observed

Diffraction can occur only when the wavelength of light is comparable to the size of the obstacle or the width of the slit.