Physics - Topic 4 - Waves

• What do waves transfer without transferring matter?

  Energy
• How do buoys demonstrate that waves transfer energy without transferring matter?

  Buoys remain still while waves pass by them
• What is the definition of wavelength?

  The distance between the same points on two consecutive waves
• What is amplitude in wave terminology?

  The distance from the equilibrium line to the maximum displacement
• How is frequency defined in wave physics?

  The number of waves that pass a single point per second
• What does the period of a wave refer to?

  The time taken for a whole wave to completely pass a single point
• What is a wavefront?

  The plane in which the wave travels
• What is the formula for wave velocity?

  Velocity = frequency × wavelength
• If the frequency of a wave is 10 Hz and the wavelength is 2 m, what is the wave speed?

  $v =$$f\lambda =$$10 \text{ Hz} \times 2 \text{ m} =$$20 \text{ m/s}$
• What happens to wave velocity when frequency increases?

  Velocity increases
• How does wavelength affect wave velocity?

  Increasing wavelength increases velocity
• What is the relationship between period and frequency?

  Period is inversely proportional to frequency
• What occurs when the period is smaller?

  Higher frequency and greater velocity
• What are the characteristics of transverse waves?

  • Includes light and electromagnetic waves, seismic S waves, and water waves
  • Has peaks and troughs
  • Vibrations are at right angles to the direction of travel
• What are the characteristics of longitudinal waves?

  • Includes sound waves and seismic P waves
  • Has compressions and rarefactions
  • Vibrations are in the same direction as the direction of travel
• How can you measure the velocity of sound in air using an echo?

  Make a noise at ~50m from a wall and record the time for the echo
• How can you measure the velocity of ripples on water's surface?

  Use a stroboscope to measure the distance between fixed ripples
• What happens to waves when they pass from one medium to another?

  They may be refracted, reflected, transmitted, or absorbed
• What occurs when waves pass into a more optically dense medium?

  The wave is refracted towards the normal
• What happens to the speed of a wave when it enters a denser medium?

  The speed decreases
• How does wavelength change when a wave enters a denser medium?

  The wavelength decreases
• What is the relationship between energy and frequency of a wave?

  Energy is directly linked to frequency
• What is the angle of incidence in relation to reflection?

  The angle of incidence equals the angle of reflection
• What happens to light when it reflects off a rough surface?

  It scatters in all directions
• What is transmission in wave physics?

  Waves pass through a transparent material
• What occurs during absorption of light by electrons?

  The light is absorbed and not reemitted
• What happens to light that appears green?

  Only green light has been reflected; other frequencies are absorbed
• How do different substances interact with waves based on wavelength?

  They may absorb, transmit, refract, or reflect waves
• What is the function of the outer ear?

  It collects sound and channels it down the ear canal
• What happens to sound waves when they hit the eardrum?

  The eardrum vibrates at the same frequency as the sound wave
• How do the small bones in the ear respond to sound waves?

  They vibrate at the same frequency as the sound wave
• What role do the small bones play in hearing?

  They amplify the sound waves received by the eardrum
• What happens when fluid in the cochlea moves due to compression waves?

  Small hairs lining the cochlea move and send impulses to the brain
• How does the ear respond to different sound frequencies?

  Different hairs are sensitive to different sound frequencies
• What happens when a hair in the cochlea moves due to a specific frequency?

  It releases an electrical impulse to the brain
• How does frequency relate to the energy of a wave?

  The higher the frequency, the more energy the wave has
• Why does the ear only work for a limited frequency range?

  We have evolved not needing to hear very high or low frequencies
• What is ultrasound?

  A sound wave with a frequency higher than 20,000 Hz
• What is one use of ultrasound in sonar?

  To calculate the depth by measuring the time for a pulse to reflect
• How is ultrasound used in foetal scanning?

  To create an image of the foetus and check its development