- #1

garthenar

- 35

- 8

- Homework Statement
- Two slits spaced 0.0720 mm apart are 0.800 m from a screen. Coherent light of wavelength λ passes through the two slits. In their interference pattern on the screen, the distance from the center of the central maximum to the first minimum is 3.00 mm. The intensity at the peak of the central maximum is 0.0900 W/m2.

a) What is the intensity at point on the screen that is 2.00 mm from the center of the central maximum?

b) What is the intensity at point on the screen that is 1.50 mm from the center of the central maximum?

- Relevant Equations
- λ=(ax)/D

a = distance between the two slits

x = the distance between maximums

m = which maximum your looking at (from the center)

D = the distance between the "source" (slits) and the screen

path difference

Δp = asin(θ)

= atan(θ)

= (ay/D)

y = vertical distance

phase difference

Φ = Δp (2π / λ)

= Δp k

I = 4(I_0)cos^2(Φ/2)

I'm still on part a.

I think that i may have the wrong equation for intensity.

I'm not sure I'm using the right numbers for the "first minimum".

λ=(ax)/D

since the first minimum occurs at m = 0.5 I multiplied the distance to the first minimum by 2 to get the distance to the first "fringe". (point of maximum constructive interference)

Δp = (ay/D)

I used the distance to the point I want the intensity at for y

Φ = Δp (2π / λ)

I = 4(I_0)cos^2(Φ/2)

Which was wrong.

Can you help me figure out where I went wrong. I've tried several variation on this.

Thank you

I think that i may have the wrong equation for intensity.

I'm not sure I'm using the right numbers for the "first minimum".

I started with getting the wavelengthI started with getting the wavelength

λ=(ax)/D

since the first minimum occurs at m = 0.5 I multiplied the distance to the first minimum by 2 to get the distance to the first "fringe". (point of maximum constructive interference)

__I then got the path difference__Δp = (ay/D)

I used the distance to the point I want the intensity at for y

__Then the phase difference__Φ = Δp (2π / λ)

__And finally my intensity__I = 4(I_0)cos^2(Φ/2)

Which was wrong.

Can you help me figure out where I went wrong. I've tried several variation on this.

Thank you