Basic Properties of Waves
Define wavelength
Wavelength is the distance between two consecutive crests or troughs of a wave, represented by the Greek letter λ and measured in meters (m).
Do electromagnetic waves require a medium? Give an example.
No. Example: Light travels through the vacuum of space.
What is wave reflection?
Reflection occurs when a wave bounces off a barrier, with the angle of incidence equal to the angle of reflection.
Define ultrasound and its medical use.
Ultrasound refers to sound waves above 20,000 Hz. It is used in sonography to create images of internal body structures.
What is the speed of sound in dry air?
343 meters per second (m/s).
What is the relationship between frequency and period?
Frequency (Hz) is the number of wave cycles per second, and period (s) is the time for one complete cycle. They are reciprocals: \( f = \frac{1}{T} \).
Provide two examples each of transverse and longitudinal waves.
Transverse: Light waves, waves on a rope.
Longitudinal: Sound waves, compression waves in a slinky.
Under what conditions does diffraction occur?
Diffraction happens when a wave encounters an obstacle or slit with a size comparable to its wavelength.
How is distance calculated using the time gap between lightning and thunder?
Time gap (seconds) ÷ 3 = distance (kilometers). Example: 3 seconds ≈ 1 km.
Why do libraries use carpets to reduce noise?
Carpets absorb sound waves, reducing reflections and reverberation.
How do you measure amplitude and wavelength from a wave graph?
- Amplitude: Vertical distance from equilibrium to a crest or trough.
- Wavelength: Horizontal distance between two consecutive crests or troughs.
How are surface waves different from transverse and longitudinal waves?
Surface waves combine transverse and longitudinal motions, causing particles to move in circular paths.
Differentiate between constructive and destructive interference.
Constructive: Waves in phase combine to increase amplitude.
Destructive: Waves out of phase combine to decrease or cancel amplitude.
Explain the Doppler Effect using an ambulance siren.
As the ambulance approaches, sound waves compress (higher pitch). As it moves away, waves stretch (lower pitch).
Why does sound travel faster in water than in air?
Water is denser than air, allowing faster energy transfer through particle collisions.
Explain the statement: “Waves transfer energy, not matter.”
Waves move energy through a medium, but particles only oscillate around their equilibrium positions. Example: A floating object bobs up and down in water waves but does not travel with the wave.
Why do mechanical waves travel fastest in solids?
Particles in solids are tightly packed, allowing efficient energy transfer through collisions.
How do noise-canceling headphones use destructive interference?
They produce sound waves 180° out of phase with ambient noise, canceling it through destructive interference.
How is a sonic boom produced?
When an object exceeds the speed of sound, shock waves merge into a high-pressure wavefront, creating an explosive noise.
How can materials control reverberation time in a room?
Hard surfaces increase reflections and reverberation.
Soft materials absorb sound, reducing reverberation.
Using ( v = fλ ), if wave speed is constant, what happens to wavelength when frequency doubles?
Wavelength halves because ( λ = \frac{v}{f} \). Doubling frequency reduces wavelength to half its original value.
Compare electromagnetic and mechanical waves in terms of their ability to travel in a vacuum.
Electromagnetic waves: Can travel in a vacuum because they rely on oscillating electric and magnetic fields.
Mechanical waves: Cannot travel in a vacuum because they require particle interactions in a medium.
If two waves with equal amplitude are completely out of phase, what is the result?
Total cancellation (amplitude = 0) due to destructive interference.
Describe how bats use echolocation.
Bats emit ultrasound pulses that reflect off objects. By analyzing the echoes, they determine the location and distance of prey.
Compare how light and sound waves change speed in denser media.
Light waves: Slow down in denser media.
Sound waves: Speed up in denser media.