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Difficulty: HardWaves, Sound, and Light

Electromagnetic radiation spans a continuous spectrum of wavelengths and frequencies, with all waves traveling at the speed of light in a vacuum. What is the correct sequence of the following electromagnetic radiation bands when arranged in order from lowest frequency to highest frequency?

  1. 1Microwave radiation
  2. 2Infrared radiation
  3. 3Ultraviolet radiation
  4. 4Gamma radiation

Answer

The correct order from lowest frequency to highest frequency is Microwave radiation, followed by Infrared radiation, then Ultraviolet radiation, and finally Gamma radiation.
Electromagnetic waves propagate at c≈3×108 m/sc \approx 3 \times 10^8\text{ m/s} in a vacuum according to the relationship c=fλc = f\lambda. As wavelength decreases, wave frequency and photon energy (E=hfE = hf) increase. Arranging the given bands from lowest frequency to highest frequency yields Microwave radiation (109 to 1011 Hz10^{9}\text{ to }10^{11}\text{ Hz}), Infrared radiation (1012 to 4×1014 Hz10^{12}\text{ to }4 \times 10^{14}\text{ Hz}), Ultraviolet radiation (8×1014 to 3×1016 Hz8 \times 10^{14}\text{ to }3 \times 10^{16}\text{ Hz}), and Gamma radiation (>1019 Hz> 10^{19}\text{ Hz}).

Step-by-Step Solution

1
Recall the inverse relationship between wavelength and frequency in electromagnetic waves.
All electromagnetic waves travel at the speed of light in vacuum (c=fλc = f\lambda), meaning that frequency (ff) increases as wavelength (λ\lambda) decreases.
Determining the correct frequency sequence requires ordering the wave bands from longest wavelength to shortest wavelength.
2
Identify the band with the longest wavelength and lowest frequency.
Microwaves exhibit wavelengths between 1 mm1\text{ mm} and 1 m1\text{ m} (f≈109 to 1011 Hzf \approx 10^{9}\text{ to }10^{11}\text{ Hz}), making it the first item in the sequence.
Microwaves sit just above radio waves at the low-frequency end of the spectrum.
3
Order the intermediate bands relative to visible light.
Infrared lies below visible red light (f≈1012 to 4×1014 Hzf \approx 10^{12}\text{ to }4 \times 10^{14}\text{ Hz}), and ultraviolet lies above visible violet light (f≈8×1014 to 3×1016 Hzf \approx 8 \times 10^{14}\text{ to }3 \times 10^{16}\text{ Hz}).
Infrared has a lower frequency than ultraviolet because its photon energy is lower.
4
Identify the band with the shortest wavelength and highest frequency.
Gamma rays possess extremely short wavelengths (<10 pm< 10\text{ pm}) and the highest frequencies (>1019 Hz> 10^{19}\text{ Hz}).
Gamma rays sit at the highest-energy boundary of the electromagnetic spectrum.

Key Concept

Electromagnetic Spectrum Frequency and Wavelength Relationships
Estimated Time:1m 15s
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Topics

Waves, Sound, and Light

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