Which types of waves does the Doppler Principle apply to?

• A. Sound, Light, and Radio Waves
• B. Only Sound and Light Waves
• C. Radio Waves and Infrared Waves
• D. Only Radio Waves

Answer: (A)

The Doppler Principle applies to all types of waves, including sound, light, and radio waves. This principle describes the change in frequency or wavelength of waves in relation to an observer moving relative to the source of the waves. For example, when a sound source moves towards an observer, the sound waves compress, resulting in a higher frequency or pitch. Conversely, as the source moves away, the waves stretch, leading to a lower frequency.

The same principle is observed with light waves, where the color of light shifts depending on the relative motion of the source and the observer — this is known as redshift and blueshift in astronomy. Radio waves, which are also a form of electromagnetic radiation, demonstrate similar behavior according to the Doppler effect.

Therefore, since the Doppler Principle applies to all of these wave types, the correct answer includes sound, light, and radio waves. Other options incorrectly limit the applicability of the Doppler Principle to fewer types of waves.