Question

1. Describe the pattern for the single-slit diffraction. How does it change when the slit width changes? How does it change when the wavelength changes?

2. Describe the pattern for the double-slit interference.

3. Describe the pattern for the four-slit interference.

4. Compare the patterns of the single-slit diffraction to the double-slit interference.

Answer 1

Intensity. Principal (central Minimum Maximum 0 1) Single-slit diffraction pattern In single slit Fraunhofer's diffraction, Maximum we will obsere a wider central subsidiary bright band, of high intensity, having -3% -2ye -Xe He 21 / 3 on both sides o- narrower alternately e slit width dark and bright bands A wavelength of decreasing intensities o angular position (from screen center) When slit width is decreased (e is reduced) the angle o incrposes ( esin o zama) therefore central maximum becomes wider. When wavelength , X, is dereased e decreased hense cetral maximum becomes ↑ Central. Maximum First minimas the angle narrower.

Intensity MUMMA 2X 3x bright bande ܝܢ 2. For double schit interference -37 -27 X (Young's double slit) position from We obserue Gereen center of of equal intensities along with dark bands of almost zero intensities DX DA d d. positioned alternately, (width of (width of bright Fringe) dark fringe) bd The widths of all bands (dark bright) is same in double slit interference. Each single bright fringe in double slit interference pattern is envelope of single slit diffraction pattern. 3, Four slit Interference. Primary It shows two type of maxinas, primary maximas of high intensities & secondary maximas of low intensities between positioned between primary maxinas, as shown. 8. 'I 1 maxinum second ary max. is not same goes on 4. In diffraction (single slit), intensity at minima zero, there is poor contrast between bright & dark bands, fringes (bands) are never of width & the intensity of successine bright fringes decreasing while double slit interference pattern usually have the intensity ad minima zero. The contrast is good between bight & dark fringes, width may not be same. The intensity of all bright fringes is same, of fringes may or