27il figure ex1727 shows the circular wave fronts emitted by...

27. Il FIGURE EX17.27 shows the circular wave fronts emitted by two wave sources. a. Are these sources in phase or out of phase? Explain. b. Make a table with rows labeled P, Q, and R and columns labeled r1, r2, r, and C/D. Fill in the table for points P, Q, and R, giving the distances as multiples of A and indicating, with a C or a D, whether the interference at that point is constructive or destructive. 1 R 2 Q FIGURE EX17.27

Transcript

00:01 These are out of phase.

00:12 The main way that you can tell this is that you can look at the radius of the smallest concentric circle.

00:25 So if you look at the smallest circle around 0 .1, its radius is equal to the distance between the first concentric circle.

00:41 And the second concentric circle, which is equal to the distance between the second concentric circle and the third concentric circle.

00:49 So the radii are consistent or proportional to each other.

00:57 If you look at point two, that center circle is smaller.

01:02 So it is out of phase because the radius for the smallest concentric circle around point two is half of the distance from the smallest circle to the next circle, to the next circle.

01:27 So they're out of phase.

01:32 So let's see, 26.

01:37 Okay, make a table.

01:42 So pqr, r1, r2, delta r, constructive or destructive.

02:02 Okay, so to point one.

02:09 Now i gotta be a little careful when i'm doing point two, but let's just do point one first.

02:19 Going to p is two radiuses, i mean two wavelengths.

02:25 Going to q from point one is one to three, and going to point r from point one is one to two and a half wavelengths.

02:45 Now we've got to be careful with two because the inner circle is only half of a wavelength.

02:54 So when we go to point p, i count a half plus one plus one plus a half...