The Electromagnetic Spectrum

The Electromagnetic Spectrum MDCAT MCQs with answers

9 past paper MCQs on The Electromagnetic Spectrum, from the Alternating Current unit of MDCAT Physics. The year each question appeared is shown where known; tap “Show answer” for the correct option and a short solution.

Read the notes first Practise the unit as a quiz

1.The wave that has the highest frequency & penetrating power is: (UHS MDCAT 2025)

  1. X-rays
  2. Ultraviolet rays
  3. Gamma rays
  4. Microwaves
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Correct answer: (c) Gamma rays

Gamma rays sit at the top of the electromagnetic spectrum in frequency and penetrate the most.

2.Red light is used in photographic dark room because of: (SZABMU MDCAT 2023)

  1. More frequency, less wavelength
  2. Less frequency, less wavelength
  3. Less frequency, more wavelength
  4. More frequency, more wavelength
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Correct answer: (c) Less frequency, more wavelength

Red is at the low frequency, long wavelength end, so its photons carry too little energy to expose the film.

3.The direct exposure of sun light where ozone layer is depleted will cause: (PMC MDCAT 2022)

  1. Skin cancer
  2. Sugar
  3. Corona
  4. Sun burn
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Correct answer: (a) Skin cancer

The ozone layer absorbs the ultraviolet, and without it that radiation reaches the skin.

4.In amplitude modulation what remains the same: (PMC MDCAT 2022)

  1. Frequency of the wave
  2. Amplitude of the wave
  3. Wavelength of the wave
  4. Intensity of waves
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Correct answer: (a) Frequency of the wave

In amplitude modulation the carrier frequency is held and only the amplitude is varied.

5.In frequency modulation, which of the following property of the original signal does not change: (PMC MDCAT 2022)

  1. Pitch
  2. Frequency
  3. Wavelength
  4. Amplitude
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Correct answer: (d) Amplitude

In frequency modulation the amplitude of the carrier is held steady and only its frequency is varied.

6.Energy emitted in the form of visible radiation is called: (PMC MDCAT 2022)

  1. Light energy
  2. Sound energy
  3. Tidal energy
  4. Geothermal energy
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Correct answer: (a) Light energy

Radiation the eye can see is light.

7.The electromagnetic radiation which moves with high frequency will have _______ wavelength: (PMC MDCAT 2022)

  1. Short
  2. Long
  3. Unchanged
  4. Variable
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Correct answer: (a) Short

$c=f\lambda$ is fixed, so a high frequency goes with a short wavelength.

8.Microwave is: (PMC MDCAT 2022)

  1. An electromagnetic wave
  2. Sound wave
  3. Longitudinal wave
  4. Standing wave
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Correct answer: (a) An electromagnetic wave

Microwaves lie between the radio waves and the infrared in the electromagnetic spectrum.

9.The wavelength of the electromagnetic wave having frequency of 3 kHz will be? (UHS MDCAT 2019)

  1. 120 km
  2. 100 km
  3. 80 km
  4. 140 km
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Correct answer: (b) 100 km

$\lambda=c/f=3\times10^8/3\times10^3$, that is $10^5\,\mathrm{m}$, or $100\,\mathrm{km}$.

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