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Mechanical pulses and waves IB DP Physics Study Notes

Mechanical pulses and waves IB DP Physics Study Notes - 2025 Syllabus

Mechanical pulses and waves IB DP Physics Study Notes

Mechanical pulses and waves IB DP Physics Study Notes at  IITian Academy  focus on  specific topic and type of questions asked in actual exam. Study Notes focus on IB Physics syllabus with Students should understand

  • transverse and longitudinal travelling waves

Standard level and higher level: 3 hours
Additional higher level: 4 hours

IB DP Physics 2025 -Study Notes -All Topics

Traveling waves 

  • Consider a taut rope which is anchored securely to a table:
  • You can send a single wave pulse through the rope by moving your hand up and then down exactly once:
  • Or you can repeat the motion to produce a continuous traveling wave:

FYI

Note that the rope as a whole doesn’t go to the right. The rope particles just vibrate up and down locally.

  • We can use a spring instead of a rope:
  • You can send a single wave pulse through the spring by moving your hand forward and backward exactly once (push and pull):
  • Or you can repeat the motion to produce a continuous traveling wave:

FYI

Note that the spring as a whole doesn’t travel to the right. The spring particles just vibrate left and right locally.

 

 

Traveling waves – energy transfer

  • Consider a securely anchored taut rope:
  • If we send a wave pulse through the rope, we see that when it reaches the end, it can do work on the mass:
  • Note that in this case work was done against gravity in the form of an increase in the gravitational potential energy of the mass.
  • You can think of the energy being transferred from your hand to the mass via the momentum or EK of the particles while they vibrate.

 

Transverse and longitudinal waves

  • Both the rope and the spring were examples of traveling waves, and both traveled in the +x-direction.
  • We call the material through which a wave propagates the medium. So far we have seen examples of two mediums: rope and spring steel.
  • The rope transferred its wave pulses by vibrations which were perpendicular to the direction of the wave velocity.
  • Any wave produced by vibrations perpendicular to the wave direction is called a transverse wave.
  • The spring transferred its wave pulses by vibrations which were parallel to the direction of the wave velocity.
  • Any wave produced by vibrations parallel to the wave direction is called a longitudinal wave.
  •  

PRACTICE: Categorize a water wave as transverse, or as longitudinal.

  • If you have ever been fishing and used a bobber you should know the answer:
  • Firstly, the wave velocity is to the left.
  • Secondly, the bobber vibrates up and down.
  • Thus the water particles vibrate up and down.
  • Thus water waves are transverse waves.

EXAMPLE:

  • Consider a speaker cone which is vibrating due to electrical input in the form of music.
  • As the cone pushes outward, it squishes the air molecules together in a process called compression.
  • As the cone retracts, it separates the air molecules in a process called rarefaction.Since the vibrations are parallel to the wave velocity, sound is a longitudinal wave.
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