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Difficulty: Very hardElectromagnetic Waves and Electromagnetic Spectrum

The electromagnetic spectrum consists of waves with varying frequencies, wavelengths, and photon energies, each associated with distinct physical detection mechanisms and applications. Consider the following types of electromagnetic radiation:

I. Radiation emitted by warm bodies, primarily detected using a thermopile.
II. Radiation utilized in radar systems and satellite communications.
III. Radiation emitted during nuclear decay processes, detected using a Geiger-Müller counter.
IV. Radiation responsible for sun tanning and detected by its ability to induce fluorescence on zinc sulfide screens.

Arrange these four types of electromagnetic radiation in order of increasing photon energy (from lowest photon energy to highest photon energy).

  1. 1Radiation utilized in radar systems and satellite communications
  2. 2Radiation emitted by warm bodies, primarily detected using a thermopile
  3. 3Radiation responsible for sun tanning and detected by its ability to induce fluorescence on zinc sulfide screens
  4. 4Radiation emitted during nuclear decay processes, detected using a Geiger-Müller counter

Answer

The correct sequence in order of increasing photon energy is: Radiation utilized in radar systems (Microwaves) < Radiation emitted by warm bodies (Infrared) < Radiation causing sun tanning (Ultraviolet) < Radiation emitted during nuclear decay (Gamma rays).
Microwaves possess the lowest frequency among the four types, followed by infrared radiation, then ultraviolet radiation, and finally gamma rays which possess the highest frequency and photon energy.

Step-by-Step Solution

1
Identify the region of the electromagnetic spectrum corresponding to each property and detector described.
Item I corresponds to Infrared radiation; Item II corresponds to Microwaves; Item III corresponds to Gamma rays; Item IV corresponds to Ultraviolet radiation.
Thermopiles detect thermal radiation (IR); radar uses microwaves; Geiger-Müller counters detect nuclear ionizing radiation (Gamma rays); fluorescence on ZnS is caused by UV light.
2
Relate photon energy EE to frequency ff and wavelength λ\lambda using Planck's relation E=hf=hcλE = hf = \frac{hc}{\lambda}.
Photon energy is directly proportional to frequency (E∝fE \propto f) and inversely proportional to wavelength (E∝1λE \propto \frac{1}{\lambda}).
Higher frequency radiation consists of more energetic individual photons.
3
Sequence the identified electromagnetic waves from lowest frequency to highest frequency.
Microwaves (f≈109−1011 Hzf \approx 10^9 - 10^{11}\text{ Hz}) < Infrared (f≈1011−4×1014 Hzf \approx 10^{11} - 4 \times 10^{14}\text{ Hz}) < Ultraviolet (f≈7.5×1014−3×1016 Hzf \approx 7.5 \times 10^{14} - 3 \times 10^{16}\text{ Hz}) < Gamma rays (f>1019 Hzf > 10^{19}\text{ Hz}).
This sequence reflects the fundamental order of increasing photon energy across the spectrum.

Key Concept

Electromagnetic Spectrum Spectral Regions, Detection Devices, and Photon Energy Ordering
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Topics

Electromagnetic Waves and Electromagnetic Spectrum

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