Phy chap4

• What are waves that pass through a substance called?

  Vibrations
• How are sound waves in air created?


  By making a surface vibrate, sending compression waves through the air
• What types of waves are classified as mechanical waves?


  Sound waves, seismic waves, and waves on strings
• What characterizes longitudinal waves?


  The direction of vibrating particles is parallel to the wave's travel direction
• Give an example of a longitudinal wave.


  Slinky
• How do transverse waves differ from longitudinal waves?


  In transverse waves, the direction of vibration is perpendicular to the wave's travel direction
• What are electromagnetic waves composed of?


  Oscillating electric and magnetic fields
• What happens to the electric and magnetic fields in electromagnetic waves?


  A vibrating electric field generates a vibrating magnetic field, which generates another electric field
• What is plane-polarised light?


  Light in which vibrations stay in one plane only
• Can longitudinal waves be polarised?


  No, longitudinal waves cannot be polarised
• What happens to unpolarised light when it passes through a Polaroid filter?


  The transmitted light becomes polarised
• What occurs when unpolarised light passes through two Polaroid filters?


  The transmitted light intensity changes if one filter is turned relative to the other
• What is the condition for the filters to be crossed?


  The transmitted intensity is a minimum when the filters are at 90° to each other
• What is displacement in the context of a vibrating particle?


  It is the distance and direction from its equilibrium position
• What is the amplitude of a wave?


  The maximum displacement of a vibrating particle
• How is wavelength defined?


  As the least distance between two adjacent vibrating particles with the same displacement and velocity
• What is one complete cycle of a wave?


  From maximum displacement to the next maximum displacement
• What is the period of a wave?


  The time for one complete wave to pass a point
• How is frequency defined?


  The number of cycles of vibrations per second
• What is the relationship between frequency and wavelength?


  Higher frequency results in shorter wavelength
• What is the formula for wave speed?


  $c =$$f\lambda$
• What is phase difference?


  The difference in phase between two points along a wave
• What is the formula for phase difference between two points?


  $\text{Phase difference} =$$\frac{2\pi d}{\lambda}$
• What is a ripple tank used for?


  To demonstrate wave properties such as reflection, refraction, and diffraction
• What are wave-fronts?


  Lines of constant phase in a wave
• How do waves travel in relation to wave-fronts?


  Waves travel at right angles to the wave-fronts
• What occurs during reflection of waves?


  Waves reflect off a surface at the same angle they hit it
• What happens to waves during refraction?


  Waves change direction and speed when passing across a boundary
• Give an example of refraction.


  When light passes from air into glass at an angle
• What is diffraction?


  When waves spread out after passing through a gap or around an obstacle
• How does the width of a gap affect diffraction?


  The narrower the gap, the more spread out the waves are
• How does wavelength affect diffraction?


  The longer the wavelength, the more spread out the waves are
• Why do satellite dishes in Europe face south?


  Because satellites orbit directly above the equator
• How does the size of a satellite dish affect signal strength?

  A bigger dish can receive a stronger signal due to more radio waves being reflected
• What is the trade-off with larger satellite dishes?

  A larger dish reflects waves to a smaller focus, requiring more careful alignment
• What does the principle of superposition state?


  The total displacement at a point is the sum of individual displacements when two waves meet
• What happens when a crest meets a crest in wave superposition?


  A super-crest is created, reinforcing the waves
• What occurs when a crest meets a trough of the same amplitude?


  The resultant displacement is zero, cancelling each other out
• What are stationary waves?


  Waves formed when two progressive waves pass through each other
• How are stationary waves formed on a rope?


  By fixing both ends and plucking the middle, allowing progressive waves to reflect and pass through each other