Light from a helium-neon laser is shined on a slit of width 0.02 mm a. describe

Question

Light from a helium-neon laser is shined on a slit of width 0.02 mm

a. describe qualitatively the pattern of light seen on a screen 1m away

b. how would the pattern change if the slit were 0.04 mm wide instead of .02mm

c. How woud the pattern change if the laser were shined on a round pinhole with a diameter of .02mm rather than a slit?

d. How would the pattern change if isntead of one slit, there were two slits each .02 mm wide, separated by .2mm?

e. How would the pattern in 4 be different if there were two slits each still .02 mm wide, but now separated by .4 mm?

Explanation / Answer

sin T = lamda/ a note that the width of the central diffraction maximum is inversely proportional to the width of the slit. If we increase the width size, a, the angle T at which the intensity first becomes zero decreases, resulting in a narrower central band. And if we make the slit width smaller, the angle T increases, giving a wider central band. L= screen distance y = L * lambda / a a we will observe bands b distance between bands reduce to half c Light shining through a pin hole will not appear on the screen as a pin hole. Instead, it will be a diffraction pattern of circular bright and dark bands, with a central bright band. d n?=d(x/l) where: n is Order of maxima ? is wavelength d is slit separation x is fringe separation l is distance from screen to double slit e distance between bands doubles

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