Q. A total of 26 bright and 26 dark Newton's rings (not counting the dark spot at the center) are observed when 540 lights falls normally on a plano convex lens resting on the flat glass surface. How much thicker is the center than edges?
Q. Two speakers, 1.20 meters apart, are playing a sound of constant frequency. You detect an area of very quiet sound about 15 degrees from the middle of the speakers. Assume this is the innermost line of interference (m = 0) and that speed of sound in air is 331 m/s, find the (linear) frequency of the sound in Hz.