What happens when electrons return to a lower level energy level

How is sound energy produced a. vibrating objects b. objects being heated c. temperature differences d. stationary objects

Which of the following is a measure of the amount of light a star directly emits?               a.  luminosity    b.  intensity    c.  wavelength    d.  brightness

As seen in a us weather map, the h (or high) and l (or low) symbols indicate regions where surface air pressures are high or low, respectively, compared to surrounding areas. an h is plotted where the air pressure is highest and an l is plotted where the air pressure is lowest. proceeding outward and away from the center of a high pressure system, the air pressure "