A source S of monochromatic light and a detector D are both located in air a distance h ab...

A source S of monochromatic light and a detector D are both located in air a distance h above a horizontal plane sheet of glass and are separated by a horizontal distance x. Waves reaching D directly from S interfere with waves that reflect off the glass. The distance x is small compared to h so that the reflection is at close to normal incidence. (a) Show that the condition for constructive interference is  and the condition for destructive interference is  (Hint: Take into account the phase change on reflection.) (b) Let h = 24 cm and x = 14 cm. What is the longest wavelength for which there will be constructive interference?