Question 1

What is the difference between sound waves and light waves?

Accepted Answer

Sound waves are longitudinal pressure waves that require a medium like air, solid, or liquid to propagate, with oscillations parallel to the direction of propagation. Light waves are transverse waves with oscillations perpendicular to propagation and can travel through a vacuum. Sound waves depend on medium density and temperature, while light does not require a medium.

Question 2

How do compressions and rarefactions relate to sound wave properties?

Accepted Answer

Compressions are regions where air particles are squeezed together, while rarefactions are regions where particles spread apart. These features define the relationship between sound wave velocity and frequency. The distance between compressions is the wavelength, and frequency is the number of cycles per second. Sound speed equals wavelength multiplied by frequency, similar to how standing waves and simple harmonics operate in resonant systems.

Question 3

Why does temperature affect the speed of sound?

Accepted Answer

Sound travels through compression of particles in a medium, so air density directly affects sound speed. Air density depends on temperature, meaning warmer air has different density than cooler air. The speed of sound can be calculated using an equation that incorporates air temperature in Celsius, showing the direct temperature-dependent relationship.

Question 4

What causes the Doppler effect when a sound source moves?

Accepted Answer

When a sound source moves toward you, sound waves bunch together, increasing perceived frequency and pitch. When moving away, waves spread apart, decreasing perceived frequency and pitch. The difference between emitted and perceived frequencies at any moment is the Doppler shift. This occurs because the relative positions of sound waves change based on source motion.

Question 5

How can you measure sound wave speed in a laboratory setting?

Accepted Answer

Connect two speakers to an oscilloscope and function generator, then adjust frequency to 5 kHz. Slide one speaker until waves are in phase, record the distance, then continue sliding until in phase again. Subtract distances to find wavelength, then multiply by frequency to calculate speed. Repeat at different frequencies like 8 kHz and 3 kHz to verify results.

Question 6

How does the Doppler apparatus demonstrate frequency changes during motion?

Accepted Answer

A Doppler apparatus swings in circles while a microphone records at a fixed distance. As the apparatus approaches the microphone, observers hear higher pitch and the oscilloscope shows increased frequency. As it moves away, pitch decreases and frequency drops on the oscilloscope. This visual and auditory demonstration clearly shows how motion affects perceived frequency.

Question 7

What are practical applications of the Doppler effect in medicine and music?

Accepted Answer

Doppler ultrasound uses frequency shifts to measure blood flow velocity in vascular assessment. A handheld probe emits ultrasound that reflects off blood cells, with frequency changes indicating flow speed. In music, wind instruments like trumpets use pressure wave resonance inside tubes to produce sound. Only wavelengths and frequencies fitting inside the tube resonate, creating the instrument's tone.

Sound Waves and Doppler Shift - Assessment Quiz