Diffraction Grating Experiment || LASER Grating Experiment by He-Ne LASER
Channel: V H Apni Physics
Date: 2014-02-01

Diffraction Grating Experiment, (LASER Grating Experiment) is performed in Physics labs with given apparatus. Grating having 15000 lines per inch, and Laser is He-Ne gas LASER. 

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Explaination:
What is the diffraction grating what diffraction of light diffraction grating formula b tech 1st-year physics lab experiment grating element below given diffraction grating theory order of diffraction you use in the calculation as shown below? That is sometimes known as diffraction grating viva questions to download the diffraction grating pdf visit the website mentioned above for full details. 

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 How to find LASER (Light Amplification by Stimulated Emission of Radiation) wavelength using a  diffraction grating viva questions. For this just take a LASER source, a grating (here grating have 15000 lines per inch), and a screen to observe the diffraction pattern. 

When a LASER light passes through the Grating its diffracted and a pattern develops on the screen with central maxima. Diffraction is a phenomenon of light, in which wave light bends at the edges of an obstacle, if and only if the size of the obstacle is comparable to the wavelength of the light. These diffracted wave superimpose further and a constructive interference appears on the screen. 

If your aim is to find the wavelength by this experiment then, first find the single slit width; that is known as grating element and denoted by "d". This you can find out from the lines that are mentioned on the grating as here 15000 LPI. One inch is 2.54 cm so 15,000 lines are in 2.54 cm so one line will be equal to 2.54/15000 cm. This is 1.69x10^ (-4)cm approximately. 

We have to use nk=2d sin theta
where k is the wavelength; that is to be found from observation
n= is the order of diffraction
d= is the grating element
and theta is the angle between the line (distance between the screen and grating) and first maxima on either side, if observation is for first order.

we have already find out the "d" grating element, n=1 for first order now we have to find the "theta" that can be find out using the "Tan theta" i.e. basically ratio of the distance from central maxima to the first-order maxima (you can say Y) and the distance between screen and grating that is D. Now "tan theta = Y/D" from this you can find the theta which can be used to calculate the value of "sin theta". Now you can put these values and find the result for wavelength (lambda). 

You can take different observations for the "theta"....by varying the distance "D" and "Y". Take the average and find the wavelength.
Now compare this result with the standard value of the laser light and check the percentage error. Your % error is the result of varying designing parameters of the LASER (Light Amplification by the Stimulated Emission of Radiation) and manual error.  diffraction grating viva questions

Frequently Asked Questions Covered here;
Which laser is used in diffraction grating experiment?
What is the principle of grating experiment?
What is a diffraction grating experiment?
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Why is it called diffraction grating?
Why do we use a diffraction grating in this experiment?
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