Diffraction TEXT ................Resolution TEXT
Diffraction is appreciable if the wavelength is of the same order of magnitude as the opening or bigger. However, if the wavelength is much smaller than the opening size diffraction is neglible Intensity of the wave has a inverse square relationship. I=P/(4pi*r2) = Power/Surface area of a sphere. Destructive interference takes place if bsinx = n(wavelength), n = 1, 2, 3, ... Since the angle x is typically small sinx = x. And x = wavelength/b. If the aperture is circular x = 1.22wavelength/b HW. PG 265: 14. Be sure you can do the proof for singleslit. DOUBLE SLIT: Separation of bright fringes for light of wavelength lambda ... Separation Distance of bright fringes: s = lambda*D/d. D is the distance from the double slit to the screen and d is the separation of the slits. For multiple slits or a diffraction grating n*lambda = d[sin(theta)] ... n = "order" of maximum [0 for central max, 1 for first max on each side, etc.], d = separation of slits, theta = angle for interference maximum. For diffraction gratings it is normal for N, the # of lines per mm, to be quoted. Use that value to find the spacing between lines (or slits) in meter, d = 1/N. The effect of increasing the number of slits:
Parallel Thin Film


Rayleigh Criterion Looking at the diffraction patterns created by the two: 2 objects can be just resolved if the central maximum of one pattern is formed at the first minimum of the other pattern.
In general it should be known that to resolve a small object of size s, the wavelength of light must be of the same order of magnitude as s or smaller. HW. PG 270: 17. 
