AAMC FL Practice Exam

What does the Doppler effect describe when an object is moving closer?

1. The effective wavelength is lengthened

2. The effective wavelength is shortened

3. The effective amplitude is unchanged

4. The effective frequency becomes zero

The correct answer is: The effective wavelength is shortened

When an object is moving closer, the Doppler effect describes a phenomenon where the effective wavelength of the emitted waves is shortened. This occurs because, as the source of the waves moves towards an observer, the waves are compressed, resulting in a decrease in the wavelength. As the distance between the source and observer decreases, the frequency of the waves that the observer detects increases, leading to a higher pitch in sound or a shift towards the blue end of the spectrum in light. This concept is crucial in various applications such as astronomy, where it helps in determining the movement of stars and galaxies, and in radar and sonar technology, where it aids in tracking objects in motion. Understanding the mechanics of how the Doppler effect influences wavelength and frequency is essential for students studying wave behavior and motion.