What is the difference between spatial and temporal coherence and what do we use in the youngs double slit experiment for interference
Temporal Coherence :
Simply in the case of light ; the light is more-or-less the same frequency
It's a measure of the average correlation between the value of a wave and itself delayed by T, at any pair of times. Temporal coherence tells us how monochromatic a source is.
Example of temporal coherence:
A wave containing only a single frequency is perfectly correlated with itself at all time delays. On the other hand a wave whose phase drifts quickly will have a short coherence time.
Similarly pulses of waves which naturally have a broad range of frequencies also have a short coherence time since the amplitude of the wave changes quickly.
Finally white light which has very broad range of frequencies is a wave which varies quickly in both amplitude and phase since it consequently has a very short coherence time it is often called incoherent.
Spatial Coherence :
Simply in the case of light ; the light is all travelling more-or-less in the same direction is called spatial coherence
The spatial coherence is the phase relationship between the radiation field at different points in space.
In some system such as a water waves or optics wave-like states can extend over one or two dimensions. Spatial coherence describes the ability for two points in space in the extent of a wave to interfere when averaged over time
The spatial coherence is the cross-correlation between two points in a wave for all times if a wave has only 1 value of amplitude over an infinite length it is perfectly spatially coherent.
In case of youngs double slit experiment, temporal coherence is used.
For getting interference pattern in youngs double slit experiment, the light should be monochromatic and we know that temporal coherence is the measure of monochromaticity.
Also how much monochromatic the source become, the experiment will show that much accurate interference pattern. So it says temporal coherence is used in youngs double slit experiment.
Temporal Coherence :
Simply in the case of light ; the light is more-or-less the same frequency
It's a measure of the average correlation between the value of a wave and itself delayed by T, at any pair of times. Temporal coherence tells us how monochromatic a source is.
Example of temporal coherence:
A wave containing only a single frequency is perfectly correlated with itself at all time delays. On the other hand a wave whose phase drifts quickly will have a short coherence time.
Similarly pulses of waves which naturally have a broad range of frequencies also have a short coherence time since the amplitude of the wave changes quickly.
Finally white light which has very broad range of frequencies is a wave which varies quickly in both amplitude and phase since it consequently has a very short coherence time it is often called incoherent.
Spatial Coherence :
Simply in the case of light ; the light is all travelling more-or-less in the same direction is called spatial coherence
The spatial coherence is the phase relationship between the radiation field at different points in space.
In some system such as a water waves or optics wave-like states can extend over one or two dimensions. Spatial coherence describes the ability for two points in space in the extent of a wave to interfere when averaged over time
The spatial coherence is the cross-correlation between two points in a wave for all times if a wave has only 1 value of amplitude over an infinite length it is perfectly spatially coherent.
In case of youngs double slit experiment, temporal coherence is used.
For getting interference pattern in youngs double slit experiment, the light should be monochromatic and we know that temporal coherence is the measure of monochromaticity.
Also how much monochromatic the source become, the experiment will show that much accurate interference pattern. So it says temporal coherence is used in youngs double slit experiment.
