Young\'s double slit experiment is set up to measure an unknown frequency of lig

Question

Young's double slit experiment is set up to measure an unknown frequency of light. The distance between the slits is .30 mm and the screen with the interference pattern is 4.2 m away. The distance between the central bright fringe and the next bright fringe is 6 mm.

4)  What is the unknown wavelength of light?

429 nm

489 nm

535 nm

602 nm

688 nm

5)  At what angle is the 3rd order bright fringe (relative to the central maximum)?

0.25 degrees

0.50 degrees

0.75 degrees

1.00 degrees

1.25 degrees

6)  How far is the 2nd order dark fringe from the central bright fringe?

5 mm

10 mm

15 mm

20 mm

25 mm

7)  If lower frequency light was used, what would happen to the spacing of the bright fringes?

nothing

they would spread apart

they would get closer together

8)  If the entire apparatus was placed underwater, what would happen to the spacing of the bright fringes?

nothing

they would spread apart

they would get closer together

Light of wavelength 481 nm shines through a slit of width 5.6 mm unto a screen 1.1 m away.

12)  How many total dark fringes can be seen?

8

14

18

22

26

13)  What is the width of the bright central diffraction fringe?

8 cm

19 cm

30 cm

41 cm

52 cm

14)  By how much does the previous answer change if light of wavelength 703 nm is used?

increases by about 20 cm

increases by about 9 cm

stays the same

decreases by about 9 cm

decreases by about 20 cm

Explanation / Answer

4) Given that x = 6 mm = 6*10^-3 m

but x = lamda*L/d

(6*10^-3) = lamda*4.2/(0.3*10^-3)

wavelength lamda = (6*10^-3*0.3*10^-3)/4.2 = 429 nm

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5) sin(t) = 3*lamda/d

angle t = asin(3*429*10^-9/(0.3*10^-3)) = 0.25 degrees

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6) x = (5/2)*6 mm = 15 mm

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7) they would spread apart
--------------------------------------

8) nothing

--------------------------

12) m =2* W/lamda = (2*5.6*10^-6)/(481*10^-9) = 23.2 ...so neay by answer is 22

===========================================
13) x = 2*lamda*L/d = (2*481*10^-9*1.1)/(5.6*10^-6) = 19 cm

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14) x = (2*703*10^-9*1.1)/(5.6*10^-6) = 27.6 cm

so change is increases by about 9 cm

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