Aim: The aim of this laboratory is to study Fraunhofer diffraction and thorough Fourier transform study what are the different shapes and sizes obtained of the fringes. During the duration of the laboratory we will study what are the different diffraction patterns obtained based on shape of the slit and its size. We will also take slits with variable distance between them and also see the Fraunhofer pattern obtained by grating.
Discussion of the Huygens-Fresnel principle:
This principle states that every point on a wavefront from a light source is itself the source of spherical secondary wavelets and that the sum of all of these secondary wavelets will govern the form of the wave at any successive time. The new wavefront thus formed is the…show more content… Anti-vibrating table.
2. A laser beam monochromatic in nature. It is a He-Ne laser with wavelength λ= 632.8 nm.
3. Various types of slit patterns used to form different types of fringe pattern.
4. Observation screen very far away (in our experiment it is 342 cm).
5. Measuring tape.
A laser beam is passed through different types of slit pattern and because the condition for diffraction is met (diffraction is observed when a wave encounters an obstacle or a slit that is comparable in size to its wavelength) different fringe pattern are obtained.
For a Fraunhofer diffraction to be observed, the observation screen should be practically very far away as compared to the size of the slit opening (we kept our observation screen 342 cm far away from the position of slit). Therefore, the condition for Fraunhofer diffraction are met.
Fraunhofer diffraction on the aperture types used during the class and comment on the observed diffraction patterns:
Different aperture types were used in the experiment to observe different types of Fraunhofer diffraction patterns. They are as follows:
Figure-Fringes obtained from Hexagonal…show more content… Figure- Fringes obtained from Triangular shaped aperture
Result- The intensity of this type of fringes is also centred in the middle and the fringes are primarily distributed in three directions and each one of them is extended a bit in their opposite direction. Therefore, the aperture should be something which is three sided. The only valid option in this case is a Triangle.
3. Figure- Fringes obtained from a Z-shaped aperture
Result- The intensity of this type of fringes is also centred in the middle and the fringes are distributed in 2 directions but if you look closely at the fringes which are obtained then you would observe a pattern and that would look like Z-shape. Therefore, our aperture is of a Z-shaped pattern.
Figure- Fringes obtained from a square shaped aperture
Result- The intensity of this type of fringes is also centred in the middle and the fringes are distributed in two directions and one more thing to observe is that the fringe size in the middle is equally sized in both horizontal and vertical direction. Therefore, our aperture should be something which is equal in both direction. The only valid option is a square shaped aperture.
5. Figure- Fringes obtained from a circular shaped