Wave Motion and Properties Quiz

Wave Motion

• Energy is transferred through a medium by periodic disturbances.
• Maximum density regions are called compressions, minimum density regions are called rarefactions.
• Compression and longitudinal waves are sets of pulses through a medium.
• Sound waves are compression waves, using the mechanical action of molecules to transfer energy through a medium.
• Sound cannot travel through a vacuum.
• Light waves are electromagnetic waves, detectable by the human eye.
• They can travel through a vacuum.

Properties of Waves

• All waves have amplitude, wavelength, frequency, and period.
• Amplitude is the distance between a crest and a trough (maximum and minimum displacement).
• Wavelength (λ) is the distance between two consecutive crests or troughs.
• Frequency (f) is the number of wavelengths passing a point per second.

Reflection and Refraction

• Wave direction changes when speed changes (refraction).
• Waves reflect when encountering a barrier.

Diffraction

• Waves "bend" around obstacles.
• This is observed when waves encounter edges.
• Diffraction explains how sound is heard around corners.

Interference (Superposition)

• The effect of overlapping waves is the algebraic sum of their effects.
• If waves have identical amplitude and frequency, the resultant wave's amplitude doubles
• If waves are half a phase out of sync, they cancel each other.

Standing Waves

• Formed by a wave interfering with its reflection.
• Example of standing waves: guitar strings, structural members.
• Nodes are points with zero amplitude, and antinodes are points of maximum amplitude.

Beats

• Result from almost but not quite the same frequency sound waves.
• The resulting sound fluctuates between maximum and minimum amplitudes, at a rate equal to the difference in frequencies.

Sound

• Sound waves are pressure waves.
• Humans hear frequencies between 20 Hz and 20,000 Hz.
• Intensity is determined by the sound wave's amplitude (measured in Watts/meter²).
• Intensity level is expressed in decibels (dB).
• The threshold of pain is 120 dB.
• Quality/timbre is determined by harmonics (numerical multiples of the original frequency).

Speed of Sound

• The speed of sound depends on the medium (e.g., air) and temperature.
• Sound waves travel as longitudinal, compression waves through an elastic medium.

Doppler Effect

• Change in frequency of sound due to the source's motion relative to the observer.
• Higher pitch as the source approaches, lower pitch as it recedes.