13. .127mm 14. B 13. A double slit arrangement is illuminated by a laser beam of
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Question
13. .127mm 14. B13. A double slit arrangement is illuminated by a laser beam of wavelength 633 nm. An intensity distribution pattern is produced, as shown below, on a screen that is 1 m from the slits. Here, y is the distance measured along the screen from the central intensity maximum. Determine the slit spacing of the double slit arrangement using the plot below 02 Distance along the screen Imml 14. A diffraction grating is illuminated with a 2 mW HeNe laser beam of wavelength 594 nm (orange). The resulting diffraction pattern on the screen behind the grating consists of three orange spots: one at 0 with respect to the laser beam direction, and one each at t45 You now add a different 2 mW HeNe laser beam of wavelength 633 nm (red) so that it coincides with (overlaps) the "orange" laser beam impinging on the grating (it is actually possible to do this). The new diffraction pattern consists of: A. Reddish-orange spots at 0 and t45. B. A reddish-orange spot at 0", orange spots at t45. and red spots slightly farther out. C. A reddish-orange spot at 0", orange spots at t45. and red spots slightly closer in.
Explanation / Answer
Q13.
distance of m th order maxima from the central bright fringe is given by m*lambda*D/d
where lambda=wavelength
D=distance of the screen from the slits
d=slit width
given:
lambda=633 nm
D=1 m
d=to be determined
m=1
distance from central fringe=5 mm=0.005 m
==>0.005=1*633*10^(-9)*1/d
==>d=1*633*10^(-9)*1/0.005=0.1266 mm=0.127 mm (approx)
Q14.
as both red and orange laser beam coincinde, their central maxima will also coincide
hence a reddish orange spot at 0 degree.
as before, orange spot will appear at +45 degree and -45 degrees
as distance of m th order maxima is given by m*lambda*D/d
where lambda is wavelength,
greater the lambda, greater is the distance from central maxima
hence red spots will be farther from the orange spot on both sides
hence option B is the correct solution.
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