Hello friends welcome to our blog Experimenteraweb.in In this article we give Diffraction Grating Practical Viva Question Answers : What is diffraction?, Mention thetwo types of diffraction?, What is diffraction grating?, What is the type of diffraction in the diffraction grating experiment?, What is grating element?, What will the even order spectra disappear?, What is the difference between prism and grating spectrum? Why does red colour deviate the most in case of grating?, What gives a more intense spectrum-prism or grating?, Define dispersion of light?, Describe essential part of spectrometer?, Why do we need two vernal scales?, Name two types of spectra? Cover this all questions in this article. So keep read and find your solution thanks.
Mention the two types of diffraction?
- Fresnel diffraction
- Fraunhofer diffraction
| Fresnel Diffraction | Fraunhofer Diffraction |
|---|---|
| Spherical or cylinder wavefront undergoes diffraction | Plane wavefront undergoes diffraction |
| Light wave is from a source at finite distance | Light wave is from a source at infinity |
| For laboratory conditions, convex lenses need not be used | In laboratory conditions, convex lenses are to be used |
| Difficult to observe and analyse | Easy to observe and analyse |
1. What is diffraction?
The phenomenon of bending of light waves around the edges of obstacle and their spreading into geometrical shadow of the obstacle is called diffraction of light.
2. What is diffraction grating?
It is an optically flat glass on which large number of equidistance parallel lines are ruled by a fine diamond pen/head.
3. What is the type of diffraction in the diffraction grating experiment?
Fraunhofer diffraction is involved because the source and the screen are effectively at infinite distance.
4. What is grating element?
It is the distance between the centres of any two successive ruled lines or transparent strips.
5. What will the even order spectra disappear?
They will disappear If the size of opaque cute lines and transparent strips is made equal.
6. What is the difference between prism and grating spectrum?
In grating spectrum violet colours is least deviated red colour is most deviated but in prism the reverse is true.
7. Why does red colour deviate the most in case of grating?
This is so because in case of grating i.e angle of diffraction is proportional to the wavelength of red is maximum.
8. What gives a more intense spectrum-prism or grating?
A prism gives more intense spectrum because in prism entire light is concentrated into one spectrum while in the case of grating light is distributed in the grating spectra of different orders.
9. Define dispersion of light?
The process of splitting of white light into it’s constituent colours is called dispersion of light.
10. Describe essential part of spectrometer?
collimator, prism table, telescope.
11. Why do we need two vernal scales?
To remove the error in reading due to not coinciding the axis of prism table and telescope.
12. Name two types of spectra?
- Emission spectra, Absorption spectra
- Diffraction grating
13. How the commercial gratings are made?
A commercial gratings is made by pouring the diluted cellulose acetate on the actual grating and drying it to a thin strong film. Also, commercial grating is called as replica grating. These are cheap and behave same as a diffraction grating.
14. Why is an experiment, the light is incident on the un-ruled side of the grating?
It is to avoid the refraction of light caused by the glass plate once it is diffracted.
15. Why does red colour deviate the most in the case of grating?
This is so because in the case of gratin. Angle of diffraction is proportional to the wavelength and the wavelength of red is maximum.