2. Which of the following electromagnetic waves has the highest energy?
a. Radio waves b. microwaves c. X-rays
d. gamma rays

3. If the frequency becomes higher, what becomes of the energy of a wave?
a. higher
b. lower c. neither, stays the same d. none

4. What unit of measurement is used to express the frequency of the wave?
a. Seconds b. Hertz
c. meters
d. Joules

5. What is the frequency of radio waves with a wavelength of 20 m?
a. 1.5 x 107 Hz b. 15 x 108 Hz c. 0.15 x 105 Hz d. 150 x 107 Hz​