Why Does Intensity Diminish at the Ends in Young's Double Slit Experiment?

[sparsh]

Hi...
Could anyone please tell me that why does the intensity of the interference pattern get diminished towards the ends of the screen ?

And can anyone also tell me what is the theoretical number of maxima that can be obtained in YDS experiment for a given wavelength, and slit , screen separation ?

Thanks a lot
Sparsh

 

[Astronuc]

The beam of photons (or electrons) is generally toward the slits. In the case of light there is an assumption of planar waves at the slits. The light diffracts (scatters) through the slits. The greater the scattering angle the lower the intensity because scattering is preferred at lower angles. The scattering angle increases as one moves away from the beam line or axis formed by the light source and center of double slits.

Analysis of double and multiple slit interference.
http://hyperphysics.phy-astr.gsu.edu/Hbase/phyopt/slits.html#c1