Which one of the following properties of electromagnetic waves does not change in a vacuum?
Correct answer: A. Speed
- A. Speed
- B. Wavelength
- C. Frequency
- D. All of the above
Explanation
Electromagnetic waves travel at a constant speed of approximately 3 × 10^8 m/s in a vacuum. This speed is a fundamental property of the medium (the vacuum itself) and does not change with the frequency or wavelength of the wave. Wavelength and frequency are related through the equation c = fλ, where c is the speed of light, f is the frequency, and λ is the wavelength. In a vacuum, as the frequency changes, the wavelength adjusts to maintain the constant speed of light. Therefore, the speed of electromagnetic waves is the property that does not change in a vacuum.
This question appeared on the ETEA MDCAT 2012 paper, which you can sit online with every answer explained.
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About Electromagnetic Waves
Electromagnetic waves consist of mutually perpendicular, oscillating electric and magnetic fields that also remain perpendicular to the direction of propagation. They travel through vacuum at the speed of light and include radio waves, microwaves, infrared, visible, ultraviolet, X-rays and gamma rays. Unlike mechanical waves, they do not require a material medium.
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