Electromagnetic Spectrum Quiz

Grade 11 · Science · Quiz

10 questions covering the regions of the EM spectrum, photon energy, the speed of light, and practical applications.

Questions

1. What is the speed of light in a vacuum?

   1. 3.00 × 10⁶ m/s
   2. 3.00 × 10⁸ m/s
   3. 3.00 × 10¹⁰ m/s
   4. 3.00 × 10⁴ m/s
   Show answer

   Answer: 3.00 × 10⁸ m/s

   The speed of light in a vacuum is exactly 299,792,458 m/s, commonly approximated as 3.00 × 10⁸ m/s.

2. Which region of the EM spectrum has the longest wavelength?

   1. Gamma rays
   2. X-rays
   3. Visible light
   4. Radio waves
   Show answer

   Answer: Radio waves

   Radio waves have the longest wavelengths (> 1 m) and lowest frequencies of all EM radiation.

3. What is the energy of a photon with frequency 5.0 × 10¹⁴ Hz? (h = 6.626 × 10⁻³⁴ J·s)

   1. 3.31 × 10⁻¹⁹ J
   2. 6.63 × 10⁻¹⁹ J
   3. 1.33 × 10⁻⁴⁸ J
   4. 8.00 × 10⁻²⁰ J
   Show answer

   Answer: 3.31 × 10⁻¹⁹ J

   E = hf = (6.626 × 10⁻³⁴)(5.0 × 10¹⁴) = 3.31 × 10⁻¹⁹ J.

4. Which property of a wave is directly proportional to photon energy?

   1. Wavelength
   2. Amplitude
   3. Frequency
   4. Speed
   Show answer

   Answer: Frequency

   E = hf — energy is directly proportional to frequency. Higher frequency = higher energy per photon.

5. Einstein's explanation of the photoelectric effect showed that light consists of:

   1. Continuous waves of energy
   2. Discrete packets of energy called photons
   3. Electrons oscillating in a field
   4. Longitudinal compression waves
   Show answer

   Answer: Discrete packets of energy called photons

   The threshold-frequency behavior of the photoelectric effect can only be explained if light energy comes in discrete packets (photons) with E = hf.

6. Which type of EM radiation is most associated with heat emission from warm objects?

   1. Radio waves
   2. Infrared
   3. Ultraviolet
   4. X-rays
   Show answer

   Answer: Infrared

   Objects at typical temperatures emit most of their radiation in the infrared region — this is the basis of thermal imaging cameras.

7. Visible light spans approximately which wavelength range?

   1. 1 nm – 10 nm
   2. 400 nm – 700 nm
   3. 700 nm – 1 mm
   4. 0.01 nm – 1 nm
   Show answer

   Answer: 400 nm – 700 nm

   Human vision detects wavelengths from roughly 400 nm (violet) to 700 nm (red).

8. Which EM wave is used in microwave ovens?

   1. Radio waves
   2. Infrared
   3. Microwaves
   4. Ultraviolet
   Show answer

   Answer: Microwaves

   Microwave ovens use ~2.45 GHz radiation which causes water molecules to rotate and generate heat through friction.

9. If wavelength decreases, what happens to frequency (at constant speed)?

   1. Frequency decreases
   2. Frequency stays the same
   3. Frequency increases
   4. Speed must also change
   Show answer

   Answer: Frequency increases

   c = fλ at constant c. If λ decreases, f must increase to keep the product constant.

10. Gamma rays are produced by:

    1. Burning fossil fuels
    2. Nuclear reactions and radioactive decay
    3. Reflection of visible light
    4. Electrical circuits
    Show answer

    Answer: Nuclear reactions and radioactive decay

    Gamma rays are high-energy photons emitted during nuclear transitions, radioactive decay, and in events like supernovae.

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