The photograph shows an experimental device at sandia national laboratories in new mexico. this device is a mirror that focuses sunlight to heat sodium to a boil, which then heats helium gas in an engine. the engine does the work of driving a generator to produce electricity. the sodium unit and the engine are labeled in the photo. (a) what kind of mirror, concave or convex, is being used? (b) where is the sodium unit located relative to the mirror? express your answer in terms of the focal length of the mirror.

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.