ELECTROMAGNETIC WAVE
Electromagnetic wave (EM wave) or electromagnetic radiation is a wave that is
created as a result of vibrations between an electric field and magnetic field, hence known
as ‘electromagnetic wave’. Recall Oersted’s discovery: A changing electric field produces
magnetic field. A changing magnetic field is therefore produced around a vibrating charge.
And according to Michael Faraday, the changing magnetic field will produce electric field.
A wave carries energy as it propagates, EM wave does the same, too. EM waves can travel
through anything even on vacuum, meaning they do not need any medium to travel. They
travel in a vacuum at a speed of 3x108 m/s.
There are seven different types of EM waves. They are arranged in a gradual
progression from the waves of lowest frequency to highest frequency. This arrangement of
EM waves is called electromagnetic spectrum. In order of increasing frequency, the EM
spectrum includes radio waves, microwaves, infrared, visible light, ultraviolet, X-ray, and
gamma ray.
ACTIVITY 1. WAVELENGTH RANGES OF EM WAVES
Wavelength is the distance between crest to crest or trough to trough. EM waves are
bounded at different ranges. Meaning each type of EM waves has upper and lower limits
on the spectrum. Using Figure 1, determine the wavelength ranges of each of the forms of
electromagnetic waves. Answer the given table below and the questions that follow and
submit them through the link.
Table 1 EM vs Wavelength
(13 POINTS)
FIGURE 1 – wavelength ranges of EM waves
QUESTIONS:
Q1. Which electromagnetic wave has the longest wavelength?
Q2. Which electromagnetic wave has the shortest wavelength?
Q3. Observe what happens to the wavelength of the electromagnetic waves as they
progress (goes rightward from the figure). Does the wavelength of the EM waves increase
or decrease as we go from radio wave to gamma ray?
Q4. This type of wave was discovered by famous astronomer Sir Frederick William
Herschel and has a range of 7x10-7 m to 1x10-3 m.
A. infrared
B. microwave
C. radio wave
D. visible light
Q5. Which of the following electromagnetic waves has the least wavelength range?
A. infrared (7x10-7 m to 1x10-3 m)
C. visible light (6.22 x10-7 m to 4.55 x10-7 m)
B. x-ray (1 x10-11 m to 1 x10-8 m)
D. ultraviolet (1x10-8 m to 4x10-7 m)
Q6. Which among the following EM waves has the longest wavelength?
A. infrared
B. ultraviolet
C. visible light
D. x-ray
Q7. Which electromagnetic wave can travel the farthest distances because it has a
wavelength range of greater than 1x10-1 m?
A. gamma ray
B. microwave
C. radio wave
D. x-ray
Q8. The wavelength of microwaves ranges from 1x10-1 m to 1x10-3 m. Which of the
following has size comparable to the wavelength of microwave?
A. Bacteria
B. Coin
C. Human
D. Pin
ACTIVITY 2 – FREQUENCIES OF EM WAVES
Compare the frequencies of different EM waves. Answer the table and the questions
follow and submit them through the link.
Table 2 – EM vs Frequency
(13 POINTS)
QUESTIONS:
Q9. Which among the EM waves has the highest frequency?
Q10. Which among the EM waves has the lowest frequency?
Q11. The energy of an EM wave also depends on its frequency, which means waves with higher
frequency has higher energy too. Which among the EM waves has the highest energy?
Q12. Which among the EM waves has the lowest energy?
Q13. What happens to the frequency of the electromagnetic waves as it progresses? Does the
frequency of the EM waves increase or decrease as we go from radio wave to gamma ray?
Q14. What is the frequency range of infrared radiation?
A. 3 x 109 Hz to 3 x 1011 Hz
C. 3 x 1014 Hz to 3 x 10 15 Hz
11
14
B. 3 x 10 Hz to 4 x 10 Hz
D. 3 x 1016 Hz to 3 x 10 19 Hz
Q15. A visible light has a frequency of 6.3 x1014 Hz. What is the color of light?
A. blue
B. green
C. red
D. yellow
Q16. Which among the following EM waves has the HIGHEST frequency among others?
A. infrared
B microwave
C. ultraviolet
D. x-ray
Q17. Which of the following EM waves has the LEAST amount of energy?
A. gamma ray
B. microwave
C. radio wave
D. x-ray
Q18. Which of the following statements is CORRECT?
A. Gamma ray has the highest frequency and the highest energy.
B. Gamma ray has the highest frequency but has the least energy.
C. Radio wave has the highest frequency and the highest energy.
D. Radio wave has the lowest frequency but has the highest energy.
ACTIVITY 3 – PROPERTIES OF EM WAVES
Now that you are already familiar with the wavelength and frequency of EM waves,
identify what happens to the wavelength, frequency and energy of the EM waves. You may
answer INCREASING or DECREASING.
(21 POINTS)
EM Waves
Wavelength
Frequency
Energy
Radio
Microwave
Infrared
Visible
Ultraviolet
x-ray
Gamma
QUESTIONS:
Q19. Which has shorter wavelength?
X-Rays or Gamma rays
Q20. Which has higher frequency?
Visible light or Ultraviolet
Q21. Which has more energy?
Radio waves or Infrared
Q22. Which has longer wavelength on visible light?
Green Light or Blue Light
Q23. Which has lesser frequency?
Microwave or Gamma ray
Pick out the word that will make the statements correct. Write your answer on a separate
sheet of paper.
The electromagnetic spectrum is the arrangement of Q24 (electromagnetic waves,
ultraviolet radiation), which are waves that are created with changing electric field and
Q25 (electric charge, magnetic field). EM waves travel on Q26 (air, vacuum) at a constant
speed of Q27 (3 x108 m/s, 8 x103 m/s). The electromagnetic spectrum is arranged in a
manner of Q28 (decreasing, increasing) wavelength, Q29 (decreasing, increasing)
frequency and Q30 (decreasing, increasing) energy. Q31 (Gamma ray, Radio wave) has the
longest wavelength, lowest frequency and lowest energy among all EM waves.
The Q32 (radio wave, visible light) is the only EM wave that can be seen by our naked eye,
whereas Q33 (red, violet) has the longest wavelength and Q34 (red, violet) has the greatest
frequency. On the other hand, Q35 (gamma ray, radio wave) has the shortest wavelength
and highest frequency; which carries the highest Q36 (energy, wavelength) among all EM
waves. Therefore Q37 (gamma ray, radio wave) has the lowest ionizing radiation, while
Q38 (gamma ray, radio wave) has the highest ionizing radiation.
Figure 2 – frequencies of different EM waves