In the double-slit experiment of figure a below, monochromatic red light of wave
ID: 2155270 • Letter: I
Question
In the double-slit experiment of figure a below, monochromatic red light of wavelength 650 nm illuminates the two parallel narrow slits S1 and S2. The slits are d = 7.45 ?m apart. Waves from the slits (which extend into and out of the page) combine at P, an arbitrary point on screen C at distance y from the central axis. The angle ? serves as a convenient locator for P. For D d, we can approximate rays r1 and r2 as being parallel, at angle ? to the central axis (figure b). (a) Calculate the angular deviation ? of the third-order (for m = 3) bright fringe in radians. (b) What is this value in degrees?
Explanation / Answer
a)x=3=yd/D
y=0.2617D
=Tan-10.2617=0.256 radians.
b)=14.67 degrees