00:01
Question 33 is asking us to compare the light gathering power of a 4 inch telescope to that of a 16 inch telescope.
00:10
So the light gathering power of a telescope, if you remember, is equal to the area of the aperture.
00:21
I'm going to call light gathering power lgp and the area of the aperture, big a, of little a.
00:29
Now, the area of the aperture can be found by taking the area of the main lens, which the aperture is.
00:43
So that's going to be pi times d over 2 squared for both of our telescopes here.
00:54
Now let's take the area of our 4 inch aperture.
00:59
That is going to be equal to pi times 4 over 2.
01:08
4 is the diameter of our aperture in inches.
01:14
And multiplying all that together, we get pi times 2 squared, which is equal to 4 pi.
01:27
I'm just going to keep pi as a separate value, so our solutions look less messy.
01:37
You'll see that it doesn't matter if we multiply through by pi anyway.
01:42
And the next, we're going to look at the area of the 16 -inch aperture...