Interference and Bright Fringes (a) The screen on the right in the drawing has a

Question

Interference and Bright Fringes

(a) The screen on the right in the drawing has a fixed width and is centered on the midpoint between the two slits on the left. Should the screen be moved to the left or to the right to ensure that the third-order bright fringe does not lie on the screen?

The screen should be moved to the right. The screen should be moved to the left.


(b) Do fewer bright fringes lie on the screen when the distance L between the double-slit and the screen is smaller or larger, or is the number of bright fringes on the screen independent of L? Fewer bright fringes lie on the screen when L is larger. Fewer bright fringes lie on the screen when L is smaller. The number of bright fringes on the screen independent of L.




The wavelength used in a Young's double-slit experiment is 625 nm. The separation between the slits is d = 1.4 10-5 m, and the total width of the screen is 0.20 m.


(c) What is the algebraic expression for tan %u03B8, which is the tangent of the angle %u03B8 that locates the angular position of the last bright fringe on the screen on either side of the central bright fringe? Express your answer in terms of the distance y (see the drawing) and distance L between the double-slit and the screen.
tan %u03B8 =


(d) What is the algebraic expression for the integer variable m that specifies the order of a bright fringe? Express your answer in terms of the separation d between the two slits, the sine of the angle%u03B8 that locates the angular position of a bright fringe, and the wavelength %u03BB.
m =


(e) Determine the number of bright fringes that fall on the screen to one side of the central bright fringe when the distance between the double-slit and the screen is L = 0.14 m. Do not include the central bright fringe in your counting. Do this by calculating the integer variable m that specifies the order of the last bright fringe on the screen to either side of the central bright fringe.
Number of bright fringes =

(f) Determine the number of bright fringes that fall on the screen to one side of the central bright fringe when the distance between the double-slit and the screen is L = 0.59 m. Do not include the central bright fringe in your counting. Do this by calculating the integer variable m that specifies the order of the last bright fringe on the screen to either side of the central bright fringe.
Number of bright fringes =

Explanation / Answer

c) tan theta = y/L

d) m lambda = d sin theta

m = d sintheta/lambda

e) largest m when theta = 90

m = d/lambda =1.4E-6/625.0E-9=2.24

so answer is 2

f) same answer as e) so 2

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