The document discusses single slit diffraction, describing how light bends as it passes through a narrow opening, resulting in a diffraction pattern. It explains the formation of intensity maxima and minima by analyzing the interference of wavelets originating from segments of the slit. The key relationships for calculating the angles of dark fringes in the pattern are also presented.

2. 1. DIFFRACTION
2. SINGLE SLIT DIFFRACTION
3. ANALYSING SINGLE SLIT DIFFRACTION
4. CONDITION FOR DIFFRACTION MINIMA AND
MAXIMA
5. INTENSITY DISTRIBUTION OF DIFFRACTED
LIGHT

3.  Diffraction is the slight bending of light as it
passes around the edge of an object. The amount
of bending depends on the relative size of the
wavelength of light to the size of the opening.

4.  When light passes
 through a small slit,
 it spreads out and
 produces a diffraction
 pattern showing a
 principle peak with
 subsidiary maxima
 and minima of
 decreasing intensity.

5. 
 FIG. EXPERIMENTAL SETUP OF SINGLE SLIT
DIFFRACTION.

6. DIFFRACTION BY SINGLE SLIT

7. 

 For an open slit of width a, subdivide the opening into
segments and imagine a Hyugens wavelet originating
from the center of each segment. The wavelets going
forward (q=0) all travel the same distance to the screen
and interfere constructively to produce the central
maximum.

8.  Now consider the wavelets going at an angle such that
l = a sin q = a q. The wavelet pair (1, 2) has a path
length difference Dr12 = l/2, and therefore will cancel.
 The same is true of wavelet pairs (3,4), (5,6), etc.
Moreover, if the aperture is divided into p sub-parts,
this procedure can be applied to each sub-part.
 This procedure locates all of the dark fringes.

9. 

p  sin   ; p

1, 2, 3,
a
p p th
(angle of the p dark fringe)

10. When the light is diffracted by a single slit then a diffraction pattern is
formed having a central maxima and subsidiary principle maxima and
minima as shown in the above figures.