# Diffraction interference

3 de Jul de 2021
1 de 15

### Diffraction interference

• 1. Represented By: Arijit Dhali
• 2. Content  Abstract  Keywords  Introduction  Diffraction  Interference  Comparison Chart  Key Differences  Conclusion  References
• 3. Abstract In this presentation, our aim is to distinguish the difference between diffraction and interference of light Throughout this presentation we will gather the basic knowledge about the topic . This presentation is a team work and every member is associated with this presentation has collected the data from various trusted sources.
• 4. Keywords  Diffraction  Interference  Constructive Interference  Destructive Interference  Fringes  Superposition  Wavefront  Wavelet
• 5. Introduction The crucial difference between diffraction and interference is that diffraction of light occurs due to the superposition of secondary wavelets that generates from various parts of a wave front (simply put spreading of light when the beam passes through the slit). As against interference is the result of the superposition of light waves from 2 coherent sources. Another important difference between the two is that the intensity of all the bright fringes is not the same in the case of diffraction however it is same in case of interference. In this session, we will discuss some other parameters that distinguish the two.
• 6. Diffraction  Diffraction is the phenomenon of spreading of the light wave when it passes through a slit or any small gap.  But it is noteworthy here that the wavelength of the wave must be comparable with the dimensions of the slit.  As in the case of the large opening, the light wave will not bend at the edges. While in case of smaller opening the bending is quite noticeable.  But for the very small dimension of the slit, the opening acts as a separate source and thus allows the spreading of the wave over the entire surface after the slit.
• 7. Diffraction of Light Waves Diffraction Pattern
• 8. Interference  Interference is the act of superposition of two or more light waves emitted by two coherent sources travelling in the same medium. We know coherent sources provide a light wave of the same frequency and constant phase difference.  So, two waves that are coherent in nature superpose each other when they cross each other. Thus the superposition of the waves gives algebraic addition of the disturbances due to separate waves.  It is to be noted here that the intensity of the resultant wave relies on the amplitude and phase relation of the two-component waves.
• 9. Constructive Interference  When the two superposing waves are of the same amplitude and phase then the intensity of the resultant wave will be higher than the two separate waves.  More specifically the amplitude of the resultant wave will be twice the amplitude of the waves that are going to be superposed.  This is called constructive interference. Destructive Interference  If the two superposing waves have the same amplitude but are of opposite phase then the intensity of the resultant wave will be lesser than the two separate waves. The amplitude of the two waves will be added but as the two are in opposite phase thus the two cancels each other.  This is called destructive interference.
• 10. Constructive Interference Destructive Interference
• 11. Comparison Chart Basis for Comparison Diffraction Interference Basic Occurs due to superposition of secondary wavelets. Occurs due to superposition of light waves from two sources. Fringe Intensity Not same for all the fringes. Same for all the fringes. Width of fringes Unequal Equal Fringe spacing Non-uniform Uniform Slit or obstacle Required Not required Direction of wave propagation Gets changed after being diffracted. Remains unchanged after getting superposed. Contrast between maxima and minima Poor Good
• 13. Conclusion So, from the above discussion, it is clear that interference is the outcome of superposition while diffraction is the consequence of spreading of the light wave.
• 14. References  https://circuitglobe.com/difference-between-diffraction-and-interference.html  https://en.wikipedia.org/wiki/Diffraction  https://en.wikipedia.org/wiki/Wave_interference  Engineering Physics By Dr. Moumita Mukherjee