Introduction to diffraction:
The wave nature of the light is further confirmed by the phenomenon of diffraction. The word diffraction is derived from the Latin word diffracts which means break to pieces. When the waves are encountering obstacles they bend round the edges of the obstacles if the dimensions of the obstacles are comparable to the wavelength of the waves. The bending of waves around the edges of an obstacle is called diffraction.
The diffraction may be take place in single or multiple slits. Here we are going to see about the diffraction by considering the passage of waves through the opening. When the opening is large compared to the wave length the waves do not bend round the edges which is given as,
When the opening is small, the bending effect round the edges is noticeable. When the opening is very small the waves spread over the surface behind the opening. The opening appears to act as an independent source of waves which propagate in all direction behind the opening.
Diffraction in multiple slit:
Here we are going to discuss about the diffraction at multiple slits. We have seen the narrow slit gives a diffraction pattern considering of a principal maximum flanked by secondary maxima of lower intensity. In case of the multiple slit, each slit produces the similar diffraction effects in the same direction and the observed pattern is crossed by a number of interferences fringes. The regions of first order, second order, etc. maxima contain equally spaced fringes but they will be progressively fainter.
The envelope of the intensity variation of the interference fringes is identical to that of the diffraction pattern due to a single slit. In general IS is the intensity at a point due to interference of light from multiple slits and Id is the intensity due to diffraction of a single slit, then the resultant intensity I is given by,
I = Id `xx` IS
Hence if Id=0 at any point, then I=0 at that point irrespective of the values of IS. The intensity and sharpness of the principal maxima increase and those of the secondary maxima decrease.
When the slits are large in number, bright narrow lines are visible on a dark background . The greater the number of slits and the closer they are the narrower and brighter are the lines on the screen. Bringing the slits closer results, of course, in an increase in the distance between the lines on the screen.
The wave nature of the light is further confirmed by the phenomenon of diffraction. The word diffraction is derived from the Latin word diffracts which means break to pieces. When the waves are encountering obstacles they bend round the edges of the obstacles if the dimensions of the obstacles are comparable to the wavelength of the waves. The bending of waves around the edges of an obstacle is called diffraction.
Diffraction
Diffraction in opening:The diffraction may be take place in single or multiple slits. Here we are going to see about the diffraction by considering the passage of waves through the opening. When the opening is large compared to the wave length the waves do not bend round the edges which is given as,
When the opening is small, the bending effect round the edges is noticeable. When the opening is very small the waves spread over the surface behind the opening. The opening appears to act as an independent source of waves which propagate in all direction behind the opening.
Multiple slit diffraction
Diffraction in multiple slit:
Here we are going to discuss about the diffraction at multiple slits. We have seen the narrow slit gives a diffraction pattern considering of a principal maximum flanked by secondary maxima of lower intensity. In case of the multiple slit, each slit produces the similar diffraction effects in the same direction and the observed pattern is crossed by a number of interferences fringes. The regions of first order, second order, etc. maxima contain equally spaced fringes but they will be progressively fainter.
The envelope of the intensity variation of the interference fringes is identical to that of the diffraction pattern due to a single slit. In general IS is the intensity at a point due to interference of light from multiple slits and Id is the intensity due to diffraction of a single slit, then the resultant intensity I is given by,
I = Id `xx` IS
Hence if Id=0 at any point, then I=0 at that point irrespective of the values of IS. The intensity and sharpness of the principal maxima increase and those of the secondary maxima decrease.
When the slits are large in number, bright narrow lines are visible on a dark background . The greater the number of slits and the closer they are the narrower and brighter are the lines on the screen. Bringing the slits closer results, of course, in an increase in the distance between the lines on the screen.
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