Physics 60 Optics: Double Slit Interference (12 of 25) Find Distance, Intensity to Central Maximum

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In this video I will find the distance and the intensity (at half-way) from the central maximum to the 1st minimum.

[sammyapsel]

something doesn't add up:
If d*sin(theta) = lambda/2,
then plugging in for phi = d*sin(theta)/lambda * 360 = 1/2 * 360 = 180
Which means that the cos(phi/2)^2 is actually cos(90)^2 which is 0 which is what you would expect for a minimum.

[YedaiHomeostatico]

So intensity is not probability because the peaks have the same intensity no matter how far they are?

[briabree]

When I multiply your values, I'm getting 1.8*10^13
Not 0.5. why is this so???

[arminbay]

Hi. So would the only place where phi equals=0 be at the central maximum?