From left, a large candle A, a point C, a small candle B, a double convex lens D. A line passes below the base of the A and B, through C, and through the center of D. An eye looks left and up from below the line to the right of the lens. Dotted lines pass from the top of the large candle to the dotted center of the lens. Solid lines pass from the top of the small candle to the dotted centerline of the lens and then turn and pass down and right to the eye. Refer to the diagram to the left and use the drop-down menus to identify the parts of a magnifying glass. Label A: VIRTUAL IMAGE Label B: OBJECT Label C: FOCAL POINT

Two loudspeakers, 5.5 m apart and facing each other, play identical sounds of the same frequency. you stand halfway between them, where there is a maximum of sound intensity. moving from this point toward one of the speakers, you encounter a minimum of sound intensity when you have moved 0.33 m . assume the speed of sound is 340 m/s.part a) what is the frequency of the sound? part b) if the frequency is then increased while you remain 0.21 m from the center, what is the first frequency for which that location will be a maximum of sound intensity? express your answer to two significant figures and include the appropriate units.