Question

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1. With the slit vertical, in which direction does the light spread out by diffraction?

2. Describe the appearance of the single slit diffraction pattern for a narrow slit and for a wider slit.

3. For the double slits, what happens to the interference fringes as the slit separation is increased? Is this consistent with equation 1?

4. Calculate the slope from any pair of the slit separation and fringe separation, then calculate the wavelength from the slope. Use the formulas shown below the table. Enter the values below the table as well. What is the percentage difference between the values?

5. Calculate the wavelength of the red laser from the fringe separation, etc., and compare with the value printed on the laser by calculating the percentage difference.

6. What is the effect of wavelength on the fringe separation? Is this consistent with equation 1?

Answer 1

For vertical Slits , the light spreads out horizontally either side of the incident beam into a pattern called diffraction pattern. d The width of the diffeaction maximam is inversely proportional to the width of the slet, ne diffraction fringe width increases for narrow slet and decreases for wider slet. For double slit the interference width of fringes is ß= AD where t= Wavelength of light D = Slit to screen distance Slet a separation So, fringe width B is inversly proportional to the frage Seit separation d. So fringe width increase as we decrease Slit width d and fringe width decrease as we increase skit Separation. plot the fringe width (B) vs (d) inverse of seit sparation we will get a stessa straight line of slope AD so if wave length = We can also calculate x directly > x= If we use longer wavelength, fringe width (B) increases. fringe width (B) decreases. now if WE = m = then m be the slope of that line where D= slit to screen distance. Bd If we use Shorter wavelength