The Sears Tower in Chicago is 443 m tall. Joe wants to set the world’sstair climbing record and runs all the way to the roof of the tower. If Joe’saverage upward speed is 0.60 m/s, how long will it take Joe to climb fromstreet level to the roof of the Sears Tower?

Which statement best describes who the period and frequency of electromagnetic was change between gamma rays and microwaves? a) the period and frequency stay the same. b) the period increases and the frequency decreases. c) the period decreases and the frequency increases. d) the period increases and the frequency increases.

If two parallel light rays hit a mirror, they will not be parallel to each other after they reflect.

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