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658.


Problem 46.15 (RHK)


(a)We have to show that the values of at which intensity maxima for single-slit diffraction occur can be found exactly by differentiating

with respect to and by equating it to zero. This gives the condition

(b) The values of satisfying this equation can be found by plotting graphically the curve and the straight line and finding their intersection. (c) We have to find the (nonintegral) values of m corresponding to successive maxima in the single-slit pattern. We may note that the secondary maxima do not lie exactly halfway between minima.





Solution:           Click For PDF Version

(a)

As

,

the condition for maxima of the function is

We have

(b)

Solutions of the equation

are:

If we expect maxima to occur at midpoints of successive minima, then the locations of secondary maxima will be determined by the relation

we are leaving out the central maxima, which corresponds to

The deviations from the midpoint approximation can be seen from first two values of , which correspond to and .

From the above calculations, we note that the secondary maxima lie do not lie at the midpoints of successive minima, but only closely to the midpoints.