Waves and Sound Waves Flashcards
What is a wave, and what are its types?
A wave is a disturbance that transfers energy through a medium.
* Mechanical waves: Need a medium, cannot travel through a vacuum (e.g., sound waves, water waves, P-waves).
* Electromagnetic waves: Do not need a medium, can travel through a vacuum (e.g., light waves, radio waves).
What are transverse waves, and how do they differ from longitudinal waves?
- Transverse waves: Particles vibrate perpendicular to wave propagation, consist of crests and troughs (e.g., all waves except sound and P-waves).
- Longitudinal waves: Particles vibrate parallel to wave propagation, consist of compressions and rarefactions (e.g., sound waves, P-waves).
What happens during compression and rarefaction in longitudinal waves?
- Compression: Particles move closer, pressure increases.
- Rarefaction: Particles move farther apart, pressure decreases.
What is amplitude, and what are its units?
- Amplitude (A) is the maximum displacement from the rest position.
- Measured in mm, cm, or m.
What is wavelength (λ), and how is it measured in different types of waves?
- Wavelength is the distance between two successive crests/troughs (transverse) or two successive compressions/rarefactions (longitudinal).
- Formula: λ = total distance / number of waves.
What is frequency (f), and how is it calculated?
- Frequency is the number of waves that pass in one second.
- Formula: f = number of waves / total time.
- Unit: Hertz (Hz).
- Depends on the source of the waves.
What is periodic time (T), and how is it related to frequency?
- The time required for one complete wave.
- Formula: T = 1 / f or T = total time / number of waves.
What is wave speed (V), and how is it calculated?
- The speed at which a wave travels.
- Formula: V = λf or V = λ / T.
What are the laws of reflection?
- Angle of incidence = Angle of reflection.
- Angle of incidence: Between the incident ray and the normal.
- Angle of reflection: Between the reflected ray and the normal.
What is refraction, and how does a wave behave when moving between different mediums?
Refraction is the change in direction of a wave due to a change in speed and wavelength when moving between mediums.
* Deep to shallow / rarer to denser: Bends toward the normal, speed and wavelength decrease, frequency remains constant.
* Shallow to deep / denser to rarer: Bends away from the normal, speed and wavelength increase, frequency remains constant.
What is a wavefront, and what are its types?
- A wavefront is a surface where all points have the same wave properties.
- Types: Plane or spherical.
What are the properties of sound waves?
- Mechanical and longitudinal waves.
- Need a medium to transfer (cannot travel through a vacuum).
- Consist of compressions and rarefactions.
How does the speed of sound vary in different states of matter?
Solids > Liquids > Gases
* Gases: 100-900 m/s | Air: 320-340 m/s
* Liquids: 1000-2000 m/s | Water: 1500 m/s
* Solids: 2000+ m/s | Steel: 5000 m/s
How can the speed of sound be measured using the gun and smoke method?
- Fire a pistol and start the stopwatch when smoke is seen.
- Stop timing when the sound is heard.
- Measure the distance, repeat for accuracy, and calculate speed using distance/time.
How can the speed of sound be measured using the echo method?
- Produce a sound and time the delay until it is heard again.
- Measure the distance to the reflecting surface.
- Calculate speed using (2 × distance) / time.
How can the accuracy of speed of sound experiments be improved?
- Use a larger distance between observers.
- Repeat and take an average.
How is loudness related to amplitude?
- Amplitude is proportional to loudness: larger amplitude → louder sound.
- Loud sounds have narrower compressions and wider rarefactions.
How is pitch related to frequency?
- Frequency is proportional to pitch: higher frequency → higher pitch.
- Higher pitch means more compressions and rarefactions in a given time.
What are the frequency ranges of sound waves?
- Infrasonic: f < 20 Hz.
- Audible for humans: 20 Hz to 20,000 Hz (20 kHz).
- Ultrasonic: f > 20,000 Hz.
When a wave passes from one medium to another, which property remains constant and why?
- The frequency remains constant because it is solely determined by the source
- Only the wave’s speed and wavelength change during refraction.
Under what condition does significant diffraction occur for a wave passing through a slit?
Diffraction is most pronounced when the slit width is significantly smaller to the wavelength of the wave, allowing the wave to spread out.
How does temperature affect the speed of sound in air?
The speed of sound in air increases with temperature because the air molecules move faster, leading to more rapid energy transfer.
