Topic 4 Waves

• What do waves transfer without transferring matter?

  Energy
• How is the concept of waves demonstrated in the sea?

  Buoys stay still despite waves passing 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?

  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?

  $v =$$f\lambda$
• How is wave speed calculated?

  Wave speed (m/s) = frequency (Hz) × wavelength (m)

  
• What happens to velocity when frequency increases?

  Velocity increases
• What is the relationship between wavelength and velocity?

  As wavelength increases, velocity increases

  
• How is period related to frequency?

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

  Higher frequency
• What are the types of waves and their characteristics?

  • Transverse waves:
  • Examples: Light, electromagnetic waves, seismic S waves, water waves
  • Characteristics: Has peaks and troughs; vibrations are at right angles to the direction of travel
  • Longitudinal waves:
  • Examples: Sound waves, seismic P waves
  • Characteristics: 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 solid wall and record the time for the echo to be heard, then use speed = distance/time
• How can you measure the velocity of sound using two microphones?

  Record the time difference between a sound passing from one to the other and use speed = distance/time
• How can you measure the velocity of ripples on water surface using a stroboscope?

  Use a stroboscope with the same frequency as the water waves and measure the distance between the ‘fixed’ ripples
• How can you measure wave speed by drawing a line on paper?

  Move a pencil along the paper at the same speed as a wavefront and measure the time taken to draw this line and the length of the line
• What happens to waves when they pass from one medium to another?

  They are refracted
• What occurs when a wave passes into a more optically dense medium?

  The wave is refracted at the boundary and bends towards the normal

  
• What happens to the speed of a wave when it enters a denser medium?

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

  Wavelength decreases

  
• What is the relationship between energy, frequency, and wavelength?

  If frequency is constant and speed decreases, wavelength must also decrease
• What happens to light when it reflects off a flat surface?

  It reflects at the same angle as it hits the surface
• How does the smoothness of a surface affect wave reflection?

  The smoother the surface, the stronger the reflected wave is

  
• What happens to light on rough surfaces?

  It scatters in all directions
• What is the law of reflection?

  The angle of incidence equals the angle of reflection
• Under what condition will light reflect off an object?

  If the object is opaque and not absorbed by the material
• What happens to light energy when it is absorbed by electrons?

  It is absorbed and then reemitted over time as heat
• What does it mean if a material appears green?

  Only green light has been reflected, and the rest of the frequencies in visible light have been absorbed
• How do different substances interact with waves based on wavelength?

  They may absorb, transmit, refract, or reflect waves depending on their wavelength

  
• What is the function of the outer ear?

  It collects sound and channels it down the ear canal
• What happens to sound waves as they travel down the ear canal?

  They remain pressure air waves
• What occurs when sound waves hit the eardrum?

  The eardrum vibrates as the incoming pressure waves reach it
• How does the eardrum respond to sound frequency?

  The eardrum vibrates at the same frequency as the sound wave
• What happens to the vibrations of the eardrum?

  They are transmitted to the fluid in the inner ear (the cochlea)
• What role do the small bones in the ear play?

  They act as an amplifier of the sound waves the eardrum receives
• What happens as the fluid in the cochlea moves due to compression waves?

  The small hairs that line the cochlea move too
• How do the hairs in the cochlea respond to different sound frequencies?

  Each hair is sensitive to different sound frequencies
• What happens when a hair attuned to a specific frequency moves?

  It releases an electrical impulse to the brain