Resolving Power of Optical Instruments Telescope: There is no gain or loss of energy, which is consistent with the principle of conservation of energy.
If it reduces in one region, producing a dark fringe, it increases in another region, producing a bright fringe. In interference and diffraction, light energy is redistributed. The degree to which diffraction occurs is:ĭifference between Interference and Diffraction The narrower the slit, the more diffraction there is and the shorter the wavelength the less diffraction there is. The extent to which the diffracted wave passing through the slit spreads out depends on the width of the slit and the wavelength of the waves. Effect of Slit Width and Wavelength on Diffraction Patterns If we were dealing with sound waves, then it would be very noisy at points along the barrier where the constructive interference is taking place and quiet where the destructive interference is taking place. The measurable effect of the constructive or destructive interference at a barrier depends on what type of waves we are dealing with. When the wave fronts hit a barrier there will be places on the barrier where constructive interference takes place and places where destructive interference happens. We label the place where constructive interference (peak meets a peak or trough meets a trough) takes place with a solid diamond and places where destructive interference (trough meets a peak) takes place with a hollow diamond.
The black lines show peaks in the waves emitted by the point sources and the gray lines represent troughs.
#PHYSICS LIGHT DIFFRACTION SERIES#
In the diagram we show a series of wave fronts emitted from each point. These two point sources represent the point sources on the two edges of the slit and we can call the source A and source B.Įach point source emits wavefront from the edge of the slit. Think about some of the effects of this if we analyze what happens when two point sources are close together and emit wavefront with the same wavelength and frequency. Diffraction Pattern:Įach point on the wavefront moving through the slit acts like a point source. Once the barrier blocks most of the wavefront, the forward moving wavefront bends around the slit because the secondary waves they would need to interfere with the primary waves to create a straight wavefront. Think about a wavefront impinging on a barrier with a slit in it, only the points on the wavefront that move into the slit can continue emitting forward moving waves- but because a lot of the wavefront has been blocked by the barrier, the points on the edges of the hole emit waves that bend round the edges.īefore the wavefront strikes the barrier the wavefront generates another forward moving wavefront (applying Huygens Principle). Why does this happen? If we apply Huygens principles it becomes clear. Waves diffract when they encounter obstacles. However, if the two are closer in size or equal, the amount of bending is considerable, and easily seen with the naked eye. If the opening is much larger than the light’s wavelength, the bending will be almost unnoticeable. The amount of bending depends on the relative size of the wavelength of light to the size of the opening. Diffraction is the slight bending of light as it passes around the edges of an object.
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