P12

• What are the two main types of waves?

  The two main types of waves are transverse waves and longitudinal waves.
• What is a transverse wave?

  A transverse wave is a wave in which the disturbance is perpendicular to the direction of wave propagation.
• What is a longitudinal wave?

  A longitudinal wave is a wave in which the disturbance is parallel to the direction of wave propagation.
• What is the speed of a wave?

  The speed of a wave depends on the properties of the medium through which it is traveling.
• What is the wavelength of a wave?

  The wavelength of a wave is the distance between two consecutive crests or troughs of the wave.
• What is the frequency of a wave?


  The frequency of a wave is the number of wave cycles that pass a given point per unit of time.
• What type of wave is a sound wave?

  A **longitudinal wave**
• Why might sound waves be difficult to visualize?

  Because longitudinal waves move parallel to the direction of wave propagation, making them harder to see directly
• How can a sound wave be represented to make it easier to study?

  Using a **sound generator** and **oscilloscope** to convert the sound wave into a **transverse waveform**
• What can be studied when a sound wave is displayed as a transverse wave?

  **Frequency** and **amplitude** of the sound wave
• What determines the volume level of a sound wave?

  The volume level of a sound is determined by the **amplitude** of the wave. The greater the volume, the greater the amplitude.
• What is the measurement of frequency for sound waves?

  The number of vibrations per second, measured in Hertz (Hz).
• The formula for wave speed (v)

  Wave speed (v) = frequency (f) × wavelength (λ)

  
  

  Where:

  • v is measured in m/s
  • f is measured in Hz
  • λ is measured in m
• If wave speed stays constant, how are frequency and wavelength related?

  • Increasing the frequency makes the wavelength shorter
  • Increasing the wavelength decreases the frequency
• Time Period (T) of a wave

  The time it takes for one complete oscillation or wavelength to pass. Calculated as T = 1 / frequency.
• Calculating wave speed

  Wave speed (v) = Distance / Time (m/s)
• What is the relationship between the angle of incidence and the angle of reflection for a wave?


  The angle of incidence is equal to the angle of reflection.
• Characteristics of a good reflector


  • Smooth, shiny, hard surface
  • Absorbs less energy from the wave
• Characteristics of a poor reflector


  • Matt, dull, rough, soft surface
  • Absorbs more energy from the wave
• Wave Absorption


  • When a wave hits a boundary (surface), some of the wave's energy is absorbed by the material at the boundary
  • This causes the wave's amplitude to decrease (e.g. an echo is quieter than the original sound)
  • Good reflectors (smooth, shiny, hard surfaces) absorb less energy
  • Poor reflectors (matt, dull, rough, soft surfaces) absorb more energy
• What is refraction?


  Refraction is when a wave changes speed as it crosses the boundary between two different media, causing a change in direction.
• What causes refraction?


  The change in speed of the wave as it crosses a boundary into a region of changed density causes the change in direction.
• Does the angle of incidence equal the angle of refraction?


  No, the angle of incidence does not have to equal the angle of refraction.
• Wave slows down and bends towards the normal when entering a more dense medium

  When a wave enters a medium with higher density, its speed decreases, causing it to bend towards the normal (perpendicular) to the boundary surface.
• Wave speeds up and bends away from the normal when entering a less dense medium

  When a wave enters a medium with lower density, its speed increases, causing it to bend away from the normal to the boundary surface.
• Wave slows down but is not bent when entering along the normal

  If a wave hits the boundary between two media at a 90 degree angle (normal to the surface), it will slow down or speed up, but its direction will not change (no bending).
• Wave Transmission


  A wave travelling through a substance is being transmitted. The wave will have less energy and a smaller amplitude when it leaves the substance.
• Wave Absorption


  Some of the energy of the wave will be absorbed by the material, warming up the substance. The lost energy is absorbed by the material.
• Example: Sound Wave Absorption

  The energy of a sound wave is absorbed by sound insulation as the wave travels through it.
• What do we call reflected sound?

  An echo
• Are hard or soft surfaces best at reflecting sound?

  Hard surfaces are better at reflecting sound.
• How are echoes reduced in cinemas and theatres?

  By using soft materials on the walls such as curtains.
• Name two animals that use echoes for navigation or communication.

  Bats and dolphins
• How to measure the speed of sound

  1. Measure out a known distance to a reflective surface
  2. Make a loud, single sound
  3. Time how long it takes to hear the echo
  4. Calculate speed using: Speed = distance / (1/2 × time)
• Which piece of equipment produces signals over a range of frequencies and of varying amplitudes?

  A signal generator
• Which piece of equipment converts signals into sound waves?

  A loudspeaker
• Which piece of equipment is used to study the frequency and loudness of a sound?

  An oscilloscope
• What does a louder sound look like on a wave diagram?

  The louder the sound, the greater the amplitude (height) of the sound waves.
• Relationship between sound pitch and wave properties

  • High pitch sounds have:
  • Shorter wavelength
  • Higher frequency waves
  • More waves are visible for high pitch sounds compared to low pitch sounds
• Sound transmission


  Sound waves are transmitted by the particles of the substance the sound is travelling through.