Page:Optics.djvu/164

 To make it as general as possible, let $$p$$ represent the number of reflexions within the drop; (Fig. 209.)

$$\theta$$ is of course found as before, 1, 2, 3, being put for $$p,$$ according as the question relates to the primary, secondary, or tertiary bow.

In this manner the radius of the of the lower bow, is found to be 40° 17′, that of the outermost 42° 2′. And the extreme values for the second bow, are 50° 57′, and 54° 7′.

182. It is easy to verify these results by observation, for as the center of the bows is in the line joining the center of the Sun Errata