Sound waves are traveling through the air. every ½ second, the sound waves pass a detector. which of the following choices correctly describes the period and frequency of these waves?

the frequency is ½ second, and the period is 2 hz.
the period is ½ second and the frequency is ½ hz.
the period is ½ second, and the frequency is 2 hz.
the period is 2 s, and the frequency is 2 hz.

Acarpenter builds an exterior house wall with a layer of wood 2.9 cm thick on the outside and a layer of styrofoam insulation 2.3 cm thick on the inside wall surface. the wood has k=0.080w/(m⋅k), and the styrofoam has k= 0.010 w/(m⋅k). the interior surface temperature is 19.0 ∘c , and the exterior surface temperature is -15.0 ∘c . a.)what is the temperature at the plane where the wood meets the styrofoam? celsius b.)what is the rate of heat flow per square meter through this wall? /m^2