Physics - Chapter 16

• What is a wave?

  A disturbance that moves from a source and carries energy
• What do all waves have in common?

  They oscillate
• What's amplitude?

  Maximum extent of a vibration or oscillation measured from the position of equilibrium
• What is wavelength?

  The distance between successive crests or troughs of a wave. Units: m or nm
• Frequency (f) - The number of oscillations per second. Units: Hz or 1/s
• Period (T) - The time it takes for one complete wave to pass a point. Units: S.

  T= 1/f
• Simple harmonic motion - Oscillatory motion for a system where the net force can be described by Hooke's law. The system is called a simple harmonic oscillator
• Simple pendulum - An object that has a small mass suspended from a light wire or string
• Critical damping - the condition in which the damping of an oscillator results in it returning as quickly as possible to its equilibrium position. It may overshoot the equilibrium position, but only once.
• Underdamped - The system is damped less than critical damping, the system will return to equilibrium faster but will overshoot and cross over one or more times
• Overdamped - Occurs when the approach to equilibrium is slower
• Natural frequency - The frequency at which a system would oscillate if there were no driving or damping force
• Mechanical waves - Travel only through matter and involve the motion of the particles of the matter they pass through (water and sound waves)
• Electromagnetic waves - Consist of varying electric and magnetic fields and can travel through a vacuum as well as through matter (light and radio waves)
• Transverse waves - Individual particle moves perpendicular to the direction of the wave
• Longitudinal waves - Successive regions of compression and rarefaction move along the spring. The particles of the spring move back and forth parallel to the spring
• The beat frequency is equal to the absolute value of the difference in the frequency of the two waves
• Only resonant frequencies produce standing waves
• The lowest frequency is called the fundamental frequency or the first harmonic
• Restoring force - a force in the opposite direction
• Fspring = -Kx
• velocity = wavelength x frequency
• What 2 factors affect the period and frequency of SHM?

  Mass and spring constant
• The period of a SHM is given by T= 2pi times the square root of m/k
• For small displacements, a pendulum is a SHO
• Restoring force is given b F=-mg(theta)
• arc length, s=L(theta)
• Vmax = square root (K/M) times X
• Resonance occurs when the driving frequency equals the natural frequency and the greatest response is for the least amount of damping.
• Pure transverse waves can only travel in solids
• Longitudinal waves can travel in any medium, solid, or fluid
• Nodes - a point along a standing wave where the wave has minimum amplitude
• antinodes - points on a stationary wave that oscillate with maximum amplitude.
• Intensity = power / area Units: w/m^2
• Power = energy / time