Hand by written ans.

1. Consider a double slit experiment where two waves of equal amplitude and phase originate at two points 5, and $2 and meet at a point P, where the oscillations they cause combine. The oscillation at point P is then given by Yp(t) = A cos(k[S, P] - wt) + A cos(k[S2P] - wt). (a) Use a trigonometric identity from chapter 1 to add these oscillations together and show the result can be 2 written as Yp(t) = 2A cos (kilts" - cot ) cos ( ) where I is the pathlength difference. (b) State clearly which part of this expression represents the amplitude of the oscillation at point P