Question

Difficulty: MediumElectromagnetic Waves and Electromagnetic Spectrum

A diagnostic medical device emits electromagnetic radiation with a frequency of 6.0×1018 Hz6.0 \times 10^{18}\text{ Hz} in a vacuum. Given that the speed of light in a vacuum is c=3.0×108 m/sc = 3.0 \times 10^8\text{ m/s}, what is the wavelength of this radiation, and to which part of the electromagnetic spectrum does it belong?

  1. 5.0×1011 m5.0 \times 10^{-11}\text{ m}, X-raysAnswer
  2. B
    5.0×1011 m5.0 \times 10^{-11}\text{ m}, Ultraviolet rays
  3. C
    2.0×1010 m2.0 \times 10^{10}\text{ m}, X-rays
  4. D
    1.8×1027 m1.8 \times 10^{27}\text{ m}, Gamma rays

Answer

The wavelength of the radiation is 5.0×1011 m5.0 \times 10^{-11}\text{ m}, which corresponds to X-rays.
Using the wave equation λ=cf\lambda = \frac{c}{f}, dividing 3.0×108 m/s3.0 \times 10^8\text{ m/s} by 6.0×1018 Hz6.0 \times 10^{18}\text{ Hz} yields λ=5.0×1011 m\lambda = 5.0 \times 10^{-11}\text{ m}. Radiation with a wavelength of 5.0×1011 m5.0 \times 10^{-11}\text{ m} (frequency 6.0×1018 Hz6.0 \times 10^{18}\text{ Hz}) falls in the X-ray portion of the electromagnetic spectrum.

Step-by-Step Solution

1
Identify the given values and the wave equation relating speed, frequency, and wavelength.
Speed of light c=3.0×108 m/sc = 3.0 \times 10^8\text{ m/s}, frequency f=6.0×1018 Hzf = 6.0 \times 10^{18}\text{ Hz}. Equation: c=fλ    λ=cfc = f \lambda \implies \lambda = \frac{c}{f}.
Electromagnetic waves propagate in a vacuum at speed cc.
2
Calculate the wavelength λ\lambda.
\lambda = \frac{3.0 \times 10^8\text{ m/s}}{6.0 \times 10^{18}\text{ s}^{-1}} = 0.5 \times 10^{-10}\text{ m} = 5.0 \times 10^{-11}\text{ m}.
Proper division of scientific notation terms.
3
Classify the electromagnetic spectral region based on the calculated wavelength.
Wavelengths in the range 1011 m10^{-11}\text{ m} to 108 m10^{-8}\text{ m} correspond to X-rays.
X-rays typically span frequencies between 3×1016 Hz3 \times 10^{16}\text{ Hz} and 3×1019 Hz3 \times 10^{19}\text{ Hz}.

Key Concept

Wave equation for electromagnetic waves and spectral region identification
Rate this question