9. a parallel beam of light with wavelength 633 nm, falls on two very narrow sli

Question

9. a parallel beam of light with wavelength 633 nm, falls on two very narrow slits .068 mm apart. how far apart are the fringes in the center of the pattern on a screen 3.3 m away?

12. in a double slit experiment it is found that blue light of wavelength 480 nm gives a second order maximum at a certain location on the screen. what wavelenth of visible light would have a minimum at the same location?

15. in a double slit experiment, the third order maximum for light of wavelength 480 nm is located 16 mm from the central bright spot on a screen 1.6 m from the slits. light of wavelength 650 nm is then projected through the same slits. how far from the central bright spot will the second-order maximum of this light be located?

Explanation / Answer

9) a = D*W/d = 3.3*633*10^-9/(.068*10^-3) = 3.1cm

12) Let the location be a distance x from the centre-line

For the blue light (?'=455nm) x is occupied by 2 fringes
x = 2?'*D/d .. (applying the double-slit fringe separation equ.)

For a 2nd order minima at same point, x is occupied by 1.5 (wider) fringes ..
x = 1.5?''.D/a .. (D/a = constant)

So 2?' = 1.5?'' .. .. ?'' = (2 * 480^-9m) / 1.5 = 640nm

15) n. wavelength = x . d / L

3*480*10^

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