Questions on Electromagnetic Spectrum
20 Multiple-Choice Questions: Electromagnetic Spectrum
1. Which of the following has the longest wavelength?
A) X-rays
B) Ultraviolet rays
C) Infrared rays
D) Microwaves
E) Radio waves
2. Which type of electromagnetic wave has the highest frequency?
A) Gamma rays
B) X-rays
C) Ultraviolet rays
D) Visible light
E) Radio waves
3. The part of the electromagnetic spectrum that can be detected by the human eye is:
A) Ultraviolet
B) Infrared
C) Visible light
D) X-rays
E) Gamma rays
4. Which electromagnetic wave has wavelengths shorter than visible light but longer than X-rays?
A) Infrared
B) Ultraviolet
C) Microwave
D) Gamma ray
E) Radio wave
5. Which electromagnetic wave is used in mobile phone communication?
A) Gamma rays
B) X-rays
C) Microwaves
D) Ultraviolet rays
E) Infrared rays
6. Which type of electromagnetic radiation is used to sterilize medical equipment?
A) Infrared
B) Microwaves
C) Gamma rays
D) Visible light
E) Radio waves
7. The speed of all electromagnetic waves in a vacuum is approximately:
A) 3 × 10⁶ m/s
B) 3 × 10⁸ m/s
C) 3 × 10¹⁰ m/s
D) 3 × 10⁴ m/s
E) 3 × 10² m/s
8. As the wavelength of electromagnetic waves decreases, their energy:
A) Increases
B) Decreases
C) Remains constant
D) First decreases then increases
E) Cannot be determined
9. The visible light spectrum ranges approximately from:
A) 100 nm – 300 nm
B) 700 nm – 1000 nm
C) 400 nm – 700 nm
D) 1 nm – 10 nm
E) 1 mm – 10 mm
10. Which type of electromagnetic wave is most dangerous to human tissue?
A) Radio waves
B) Infrared rays
C) Microwaves
D) Gamma rays
E) Visible light
11. The electromagnetic radiation with longer wavelength than red light is:
A) Blue light
B) Gamma rays
C) Infrared
D) Ultraviolet
E) X-rays
12. Which wave has the lowest energy?
A) Gamma ray
B) Microwave
C) Ultraviolet
D) Radio wave
E) Infrared
13. What determines the color of visible light?
A) Its amplitude
B) Its speed
C) Its wavelength/frequency
D) Its angle of incidence
E) Its polarization
14. Which of these is in the correct order from lowest to highest frequency?
A) Gamma rays, X-rays, Visible light
B) Radio waves, Microwaves, Ultraviolet
C) Microwaves, Radio waves, Infrared
D) Ultraviolet, X-rays, Infrared
E) Visible light, Gamma rays, Microwaves
15. Infrared radiation is most associated with:
A) Nuclear decay
B) UV sterilization
C) X-ray imaging
D) Heat and thermal energy
E) Magnetic resonance
16. Which electromagnetic wave is commonly used in TV and FM radio transmissions?
A) Ultraviolet
B) X-rays
C) Gamma rays
D) Radio waves
E) Infrared
17. X-rays are widely used in:
A) Night vision
B) Medical imaging
C) Cooking food
D) Radio transmission
E) Tanning salons
18. The unit of frequency in the electromagnetic spectrum is:
A) Joules
B) Meters
C) Seconds
D) Hertz
E) Newton
19. The energy of electromagnetic radiation is directly proportional to:
A) Wavelength
B) Amplitude
C) Frequency
D) Mass
E) Speed
20. Which of the following waves has the shortest wavelength?
A) Microwaves
B) Ultraviolet
C) X-rays
D) Gamma rays
E) Infrared
Answer Key with Explanations
1. E – Radio waves
Radio waves have the longest wavelength in the electromagnetic spectrum, often measured in meters or kilometers.
2. A – Gamma rays
Gamma rays have the highest frequency and therefore the highest energy.
3. C – Visible light
This is the only part of the electromagnetic spectrum that is visible to the human eye.
4. B – Ultraviolet
Ultraviolet radiation sits between visible light and X-rays.
5. C – Microwaves
Used in mobile phone and satellite communications due to their ability to penetrate the atmosphere.
6. C – Gamma rays
They are highly energetic and can kill bacteria and viruses, making them effective for sterilization.
7. B – 3 × 10⁸ m/s
All EM waves travel at the speed of light in a vacuum.
8. A – Increases
Energy is inversely proportional to wavelength and directly proportional to frequency.
9. C – 400 nm – 700 nm
Visible light spans roughly from violet (400 nm) to red (700 nm).
10. D – Gamma rays
They can cause severe cellular damage and mutations.
11. C – Infrared
Infrared has longer wavelength than red light and is perceived as heat.
12. D – Radio wave
Radio waves have the lowest energy and longest wavelengths.
13. C – Wavelength/frequency
Color is determined by specific wavelengths/frequencies within the visible spectrum.
14. B – Radio waves, Microwaves, Ultraviolet
This sequence goes from lowest to higher frequencies.
15. D – Heat and thermal energy
Infrared radiation is emitted by warm objects and felt as heat.
16. D – Radio waves
They are used for both audio and video broadcasting.
17. B – Medical imaging
X-rays penetrate soft tissue but are absorbed by bones, making them ideal for imaging.
18. D – Hertz
The unit of frequency is Hz (cycles per second).
19. C – Frequency
E = h·f, where E = energy, h = Planck’s constant, f = frequency.
20. D – Gamma rays
They have the shortest wavelengths and highest energy in the spectrum.
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