Two slits spaced 0.0720 mm apart are 0.800 m from a screen. Coherent l

William Burnett

William Burnett

Answered question

2022-01-11

Two slits are 0.800 m from a screen, separated by 0.0720 mm. The two slits allow coherent light of wavelength to pass through. The separation between the first minimum and the center of the central maximum in their interference pattern on the screen is 3.00 mm. What is the intensity at spots on the screen that are (a) 2.00 mm and (b) 1.50 mm from the center of the central maximum if the intensity at the peak of the central maximum is 0.0600 W/m2?

Answer & Explanation

Deufemiak7

Deufemiak7

Beginner2022-01-12Added 34 answers

The intensity at any point can be determined using the relation:
I=Imaxcos2(ϕ2)
where ϕ is the phase difference corresponding to the given point.
The path difference corresponding to the position y can be given by the following relation:
x=ydD
This path difference for the first minimum is equal to half of the wavelength. Hence, calculate the wavelength using the relation.
λ2=(3×103)(0.072×103)(0.800)
λ=54×108 m
Now, calculate the path difference corresponding to y=2 mm from the central maximum.
x=ydD
=(2×103)(0.072×103)0.800
=18×108 m
Now, calculate the phase difference corresponding to the path difference.
ϕ=2πλ×x
=2π54×108×(18×108)
=2π3
The intensity at the point can be determined as follows:
I=Imaxcos2(2π32)
=0.015 Wm2

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