A laser beam is incident on two slits with separation d = 0.048 mm. A screen is

Question

A laser beam is incident on two slits with separation d = 0.048 mm. A screen is placed L = 3.2 m from the slits. The wavelength of the laser light is = 1250 Å. 1 and 2 are the angles to the first and second bright fringes above the center of the screen.

25% Part (a) Express sin(1) in terms of d and .

25% Part (b) Express sin(2) in terms of d and .
25% Part (c) Express the distance between the two bright fringes on the screen, y, in terms of 1, 2 and L.
25% Part (d) Solve for the numerical value of y in meters.

Explanation / Answer

Condition for bright fringes is,

         d sin(1) = m*

         d sin(1) =1*

          sin(1) = / d

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(b)

Condition for bright fringes is,

         d sin(2) = m*

         d sin(2) =2*

          sin(2) =2 / d

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(c)

From the figure tan2 - tan1 = y / L

For small angles tan = sin

sin2 - sin1 = y / L

y = L(sin2 - sin1 )

d)y = 2 L / d - L / d = L / d = 0.0083 m = 8.3 mm

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