Question

What will happen in diffraction if obstacle size is greater than order of light striked?

Answer 1

The number of slits in the grating is very large, so
the intensity maxima are very sharp and narrow.
The peak intensities are also much higher than in
the double slit case.
• The conditions for constructive interference are
the same as those given in equation 6. However
the source in the experiment is not monochro-
matic (mercury gas discharge tube) and will now
emit a number of discrete wavelengths. The ze-
roth order (n = 0) corresponds to constructive in-
terference of all the wavelengths from the source.
Longer wavelengths will have greater diffraction
angles than shorter wavelengths. For example, red
Incident
plane
wave Grating
Equal mixture
of red and blue
l1 and l2
n = 0
n = -1
n = -2
n = 1
n = 2
Diffraction grating.
light will be diffracted more than blue light. The
entire spectrum will repeat in high orders (higher
n).
• A diffraction grating should be designed so that
even the higher orders (|n| > 0) can be observed
within the first set of minima (primary lobe) of
the diffraction pattern