# Viva Questions On Diffraction Grating Pdf Download

## Viva Questions on Diffraction Grating PDF Download

A diffraction grating is an optical device that consists of a large number of parallel slits or lines that diffract light into different directions. Diffraction gratings are widely used in spectroscopy, optical communication, and optical metrology. In this article, we will provide some common viva questions and answers on diffraction grating that can help you prepare for your lab exams or interviews.

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## What is diffraction?

Diffraction is the phenomenon of bending of light waves around the edges of obstacles and their spreading into the geometrical shadow of the obstacle. Diffraction depends on the wavelength of light and the size of the obstacle. When the size of the obstacle is comparable to or smaller than the wavelength of light, diffraction is significant and produces observable patterns.

## What are the types of diffraction?

There are two types of diffraction: Fresnel diffraction and Fraunhofer diffraction. Fresnel diffraction occurs when the source and the screen are at finite distances from the obstacle, and the wavefronts are spherical or curved. Fraunhofer diffraction occurs when the source and the screen are at infinite distances from the obstacle, and the wavefronts are plane or parallel. Fraunhofer diffraction is simpler to analyze mathematically and experimentally than Fresnel diffraction.

## What is a diffraction grating?

A diffraction grating is a plane glass plate or a mirror on which a large number of equidistant, parallel slits or lines are ruled. The slits or lines act as sources of secondary waves that interfere constructively or destructively depending on their path difference. A diffraction grating can produce a spectrum of colors when white light is incident on it, or can separate different wavelengths of light when monochromatic light is incident on it.

## What is the grating element?

The grating element, also called the grating constant, is the distance between the centers of any two successive slits or lines on a diffraction grating. The grating element determines the angular separation of different orders of spectra produced by a diffraction grating. The smaller the grating element, the larger the angular separation.

## What is the order of diffraction?

The order of diffraction, denoted by n, is an integer that indicates how many wavelengths of path difference exist between two adjacent slits or lines on a diffraction grating. The order of diffraction determines the direction or angle at which a particular wavelength of light is diffracted by a grating. The higher the order of diffraction, the larger the angle of diffraction.

## What is the condition for maxima in a diffraction grating?

The condition for maxima in a diffraction grating is given by: $$d \sin \theta = n \lambda$$ where d is the grating element, $\theta$ is the angle of diffraction, n is the order of diffraction, and $\lambda$ is the wavelength of light. This condition implies that constructive interference occurs when the path difference between two adjacent slits or lines is equal to an integral multiple of the wavelength.

## What is the condition for minima in a diffraction grating?

The condition for minima in a diffraction grating is given by: $$d \sin \theta = (n + \frac12) \lambda$$ where d is the grating element, $\theta$ is the angle of diffraction, n is any integer, and $\lambda$ is the wavelength of light. This condition implies that destructive interference occurs when the path difference between two adjacent slits or lines is equal to an odd multiple of half the wavelength.

## How to measure the wavelength of light using a diffraction grating?

To measure the wavelength of light using a diffraction grating, we need to know the grating element d and measure the angle of diffraction $\theta$ for a given order n. Then we can use the condition for maxima to calculate $\lambda$ as follows: $$\lambda = \fracd \sin \thetan$$ Alternatively, we can use a spectrometer to measure $\theta$ for different wavelengths and plot a graph of $\sin \theta$ versus $\lambda$. The slope of the graph will give the value of d/n.

## How to measure the grating element using a diffraction grating?

To measure the grating element using a diffraction grating, we need to know the wavelength of light $\lambda$ and measure the angle of diffraction $\theta$ for a given order n. Then we can use the condition for maxima to calculate d as follows: $$d = \fracn \lambda\sin \theta$$ Alternatively, we can use a spectrometer to measure $\theta$ for different wavelengths and plot a graph of $\sin \theta$ versus $\lambda$. The slope of the graph will give the value of d/n.

## What are the advantages and disadvantages of a diffraction grating over a prism?

Some advantages of a diffraction grating over a prism are: - A diffraction grating can produce higher orders of spectra, which have higher angular dispersion and resolution than a prism. - A diffraction grating can be used for any wavelength of light, whereas a prism has a limited range of transmission and suffers from chromatic aberration. - A diffraction grating is cheaper and easier to manufacture than a prism. Some disadvantages of a diffraction grating over a prism are: - A diffraction grating has lower intensity of spectra than a prism, because some light is lost in the opaque regions and in higher orders. - A diffraction grating has overlapping spectra of different orders, which can cause confusion and errors in measurement. - A diffraction grating is more sensitive to alignment and dust than a prism.

## Where can I download a PDF file of viva questions on diffraction grating?

You can download a PDF file of viva questions on diffraction grating from [this link]. This file contains 50 viva questions and answers on diffraction grating, along with diagrams and formulas. You can also find more viva questions and answers on diffraction grating from [this link] and [this link].