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Difficulty: MediumElectromagnetic Waves and Electromagnetic Spectrum

Arrange the following regions of the electromagnetic spectrum in order of decreasing wavelength (from longest wavelength to shortest wavelength).

  1. 1Microwaves
  2. 2Infrared radiation
  3. 3Ultraviolet radiation
  4. 4Gamma rays

Answer

The correct sequence from longest to shortest wavelength is: Microwaves, Infrared radiation, Ultraviolet radiation, and Gamma rays.
The electromagnetic spectrum ordered by decreasing wavelength (longest to shortest) follows the sequence: radio waves/microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays. Thus, microwaves come first with the longest wavelength, followed by infrared, ultraviolet, and finally gamma rays with the shortest wavelength.

Step-by-Step Solution

1
Recall the wave equation c=fλc = f \lambda connecting frequency (ff) and wavelength (λ\lambda) for electromagnetic waves in a vacuum.
Wavelength is inversely proportional to frequency and photon energy.
Since the speed of light cc is constant, waves with lower frequencies have longer wavelengths.
2
Identify the relative wavelengths of each specified region of the electromagnetic spectrum.
Microwaves (10−3 m−10−1 m10^{-3}\text{ m} - 10^{-1}\text{ m}) > Infrared (7×10−7 m−10−3 m7 \times 10^{-7}\text{ m} - 10^{-3}\text{ m}) > Ultraviolet (10−8 m−4×10−7 m10^{-8}\text{ m} - 4 \times 10^{-7}\text{ m}) > Gamma rays (<10−11 m< 10^{-11}\text{ m}).
Microwaves sit near the radio end of the spectrum, while gamma rays lie at the extreme high-energy end.
3
Sequence the items from longest wavelength to shortest wavelength.
Microwaves →\rightarrow Infrared radiation →\rightarrow Ultraviolet radiation →\rightarrow Gamma rays.
This arranges the waves in strict order of decreasing wavelength.

Key Concept

Electromagnetic spectrum wavelength and frequency hierarchy
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Topics

Electromagnetic Waves and Electromagnetic Spectrum

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