VCE Physics the nature of waves

1. The Nature of Waves
Energy can be transferred by the movement
of an object
e.g. Moving matter.

2. Continued
Energy can also be transferred when it is carried
through a substance.
http://www.youtube.com/watch?v=bMgBt-
UuUak
Solar Tsunami

3. Mechanical Waves
(energy through matter)
• All waves involve the transfer of energy
without a net transfer of matter.
• The substance carrying the wave is called the
medium.
• In the case of the tsunami, the medium is the
water of the ocean.
• In the case of the sound waves from the
speaker, the medium is the air.

4. Mechanical Waves
Mechanical waves are generated at a source and
must be passed through an elastic medium
Source of the sound waves
comes from vibrating guitar
string.

5. Why combine the study of waves and
light?
If waves are to be our chosen model for light then they
must appear to behave largely in the same manner as
light. That is, if a wave model for light is to be accepted
then it will need to be able to explain the known
behaviours of light. A very successful model would
illustrate all of the behaviours of light. Perfect modelling
is rare in science. Rather it is more likely that we make
use of the insight that a particular model provides and, as
was the case with our early models of the atom, use it as
a stepping-stone to furthering our understanding.

6. Sound Waves From A Speaker
http://www.youtube.com/watch?v=UU7iuJ98fR
Q&feature=related
http://www.youtube.com/watch?v=scbPKjU8S
sg&feature=related
http://www.youtube.com/watch?v=Yw4qklgNIxI
&feature=related
http://www.youtube.com/watch?v=3zoTKXXNQI
U&feature=fvw

7. Slinky Springs
• Create a single wave using a slinky spring.
• Create a continuous wave using a slinky
spring.

8. Wave Pulses and Continuous Waves
A wave pulse occurs when a single disturbance
passes through a medium
Continuous waves are
produced when there is
repetition (oscillation) at
the wave source.
Time to play with slinky springs

9. Transverse and Longitudinal Waves
Transverse waves are produced when the
direction of vibration is at right angles to the
direction of the wave energy.

10. Transverse and Longitudinal Waves
• Longitudinal (compression) waves are
produced when the direction of vibration is
parallel to the direction of the wave energy.

11. S and P waves associated with
earthquakes
Which of the S and P waves is longitudinal? Which is transverse?

12. Longitudinal Waves

13. Sound Waves are an example of
Longitudinal Waves

14. One, Two and Three Dimensional
Waves
One dimensional waves occur when energy
travels along the length of the conducting
medium.
Example: wave in spring or rope.
Two dimensional waves occur when energy
spreads in two dimensions.
Example: wave in ripple or a pond. Solar
quakes seen earlier.

15. Example of two dimensional wave
http://www.youtube.com/watch?v=2awbKQ2D
LRE

16. Three Dimensional Waves
Three dimensional waves occur when energy
spreads out in all directions.
Example: sound waves when you speak.
http://www.youtube.com/watch?v=s9GBf8y0lY0
Example: pressure waves from a bomb blast.
http://www.youtube.com/watch?v=nyaQnhvZM
xI

17. Summary
• Scientists use models to link an unknown entity or observation to something that we are familiar
with, in order to gain a better understanding of it.
• Knowledge of general wave properties will allow the possible wave nature of light to be assessed.
• Energy must be present at the source of any wave.
• All waves involve the transfer of energy without a net transfer of matter.
• A substance carrying a wave is called a medium.
• A mechanical wave is the passing of energy from one particle to the next within an elastic medium.
• A wave pulse occurs when a single disturbance is passed through a medium.
• Continuous waves are created when there is a repetitive motion or oscillation at the wave source.
Energy is carried away from the source in the form of a continuous or periodic wave.
• Longitudinal waves occur when particles of the medium vibrate in the same direction as the direction
of travel of the energy.
• Transverse waves are created when the direction of the vibration of the particle of the medium is
perpendicular to the direction of travel of the wave energy itself.

18. 7.1 Questions
Do them now…