Light and Electromagnetic Radiation Worksheet

Be sure to set up each problem correctly and show how units cancel. For questions, explain your answers clearly.

  1. What is the relationship between the frequency of light and its wavelength?

c = λ ν Wavelength and frequency are inversely proportional. When wavelength goes up, frequency goes down.

  1. What is the relationship between the frequency of light and its energy?

E = h νEnergy and frequency are directly proportional. When frequency goes up, energy also goes up. h is Planck’s constant, 6.63 x 10-34 J-s.

  1. Which color of visible light has the longest wavelength? Red
    Which color has the shortest? Violet
  1. Which color of visible light has the highest energy? Violet
    Which color has the lowest? Red
  1. What is meant by the "frequency of light"? What is the symbol & what is the SI unit for frequency?

The frequency of light is the number of cycles per second of the electrical or magnetic wave that makes up electromagnetic radiation. The symbol is the Greek letterν and the SI unit is the Hz, which is one cycle per second.

  1. Define Hz, kHz and MHz.

Hz is one cycle per second. In calculations, Hz is replaced with 1/s or s-1. kHz = kilohertz, or 103 Hz. MHz = megahertz, or 106 Hz.


  1. Sketch a diagram of a wave and label its wavelength and its amplitude.
  1. What is the frequency of blue light with a wavelength of 425 nm?

ν = = = 7.06 x 1014 s-1

  1. What is the frequency of a short-wave radio transmission with a wavelength of 20. m?

ν = = = 1.5 x 107 s-1 = 15 MHz

  1. What is the wavelength of red light with a frequency of 4.6 x 1014 s-1?

λ = = = 6.5 x 10-7 m = 650 nm

  1. Antennas designed to receive radio waves are typically one-half of a wavelength long. How long should the antenna be to receive radio waves from television station channel 2, KTVU (frequency: 55.5 MHz)?

λ = = = 5.41 m λ/2 = 2.70 m

  1. What is the energy of a radio wave from the AM broadcast band? Use the frequency of KNBR which broadcasts the San Francisco Giants games (680 kHz)?

E = h ν = 6.63 x 10-34 J-s x 680 x 103 s-1 = 4.5 x 10-28 J

  1. What is the energy of the radio signals from your cell phone? Assume the transmission frequency is 900 MHz.

E = h ν = 6.63 x 10-34 J-s x 900 x 106 s-1 = 6 x 10-25 J

  1. What is the energy of red light with a frequency of 4.6 x 1014 s-1?

E = h ν = 6.63 x 10-34 J-s x 4.6 x 1014 s-1 = 3.0 x 10-19 J

  1. What is the energy of an x-ray with a wavelength of 10-10 m?

ν = = = 3 x 1018 s-1

E = h ν = 6.63 x 10-34 J-s x 3 x 1018 s-1 = 2 x 10-15 J

  1. If a red light wave and a 1011 Hz microwave race down a 10 m tube, which one will get to the other end first? Explain your answer.

The two electromagnetic waves would reach the end of the tube at the same time. The speed of electromagnetic waves for all frequencies is the same as the speed of light because light is an electromagnetic wave.