1. PHYSICAL SCIENCE
FORCES and INTERACTIONS

2. Bell Ringer

3. Objectives ForToday:
•By the end of the day you should:

4. Agenda/Announcements!
•Homework:
Announcements:
•

5. What are waves?

6. Wave
• Definition: A disturbance that transfers energy from place to place.
• What carries waves? A medium, a medium is the material through which a wave
travels.
• A medium can be a gas, liquid, or solid.

7. NOT ALL WAVES
REQUIRE A MEDIUMTO
TRAVEL.
* But most do. Light from the sun travels through empty space.

8. What causes waves?
• Waves are created when a
source of energy causes a
medium to vibrate.
• A vibration is a repeated back
and forth or up and down
motion.

9. Types of waves: Waves are classified
according to how they move.

10. Transverse wave
• Waves that move the medium at
right angles to the direction in which
the waves are traveling is called a
transverse wave.
• Transverse means across.The highest
parts are called crests the lowest
parts are called troughs.

11. CompressionalWave
• Matter vibrates in the same
direction as the wave travels.
• Example: Slinky

12. Compressional wave
• The parts,where the coils are
close together are called
compressions, the parts where
the coils are spread out are
called rarefactions.

13. Combinations of waves
• Surface waves are a
combination of transverse and
longitudinal waves.The waves
occur at the surface between
water and air.

14. PROPERTIES OF WAVES

15. Basic Properties ofWaves
• Amplitude
• Wavelength
• Frequency
• Speed

16. DrawTransverse wave and label: crest & trough
the old Slinky song)

17. Draw a Compressional wave: label
compression& rarefaction

18. Amplitude
• Amplitude is the maximum distance the particles of the medium carrying the wave
move away from their rest positions.
• The farther the medium moves as it vibrates the larger the amplitude of the resulting
waves.The greater the amplitude the greater the amount of energy

19. Amplitude of transverse waves
• The amplitude of a transverse wave is the maximum distance the medium moves
up or down from its rest position. You can find the amplitude of a transverse wave
by measuring the distance from rest to crest or rest to trough.

20. Amplitude of a longitudinal wave.
• The amplitude of a longitudinal wave is a measure of how compressed or rarefied
the medium becomes.

21. Wavelength
• A wave travels a certain distance before it starts to repeat. The distance between
two corresponding parts of a wave is its wavelength.
• Transverse measure from crest to crest or trough to trough.
• Longitudinal measure from one compression to the next.

22. Frequency
• The number of complete waves that pass a given point in a certain amount of
time.
• AKA number of vibrations per second.
• Frequency measured in hertz (Hz).

23. Speed
• The speed, wavelength, and frequency of a wave are related to each other by a
mathematical formula.
• Speed = wavelength x frequency
• Frequency = speed/wavelength
• Wavelength = speed/frequency

24. Speed
• Waves in different mediums
travel at different speeds.
However, in a given medium
and under the same conditions
the speed of the wave is
constant.

26. WaysWaves Interact
• Reflection
• Refraction
• Diffraction
• Interference
• Constructive
• Destructive
Standing Waves

27. Reflection
• When an object or wave hits a
surface through which it cannot
pass, it bounces back.
• Angle of incidence
• Angle of reflection

28. Examples of reflection
• Mirror
• Echo
• Ball against a wall

29. Refraction is when a wave moves from one
medium into another medium at an angle, it
changes speed as it enters the second
medium which causes it to bend.The
bending of waves due to a change in speed
is called refraction.

30. Refraction
• Though all waves change speed
when they enter a new
medium. Bending occurs when
one side of the wave enters the
new medium before the other
side

31. Diffraction
• When a wave passes a barrier or moves through a hole in a barrier it bends and
spreads out.

32. Interference
• Constructive interference occurs whenever two waves combine to make a wave
with a larger amplitude.
• Destructive interference when the amplitudes of two waves combine producing a
smaller amplitude.

33. Standing waves:
• If the incoming wave and the reflected wave combine at the right places the
combined wave appears to be standing still.
• It appears to be standing in one place, even though it is two waves interfering as
they pass through each other.

35. Nodes and Antinodes
• Nodes: at certain points, destructive
interference causes the two waves to
combine and produce an amplitude
of zero.
• Antinodes are the points of
maximum energy. The crests and
troughs of a standing wave.

36. Resonance
• Most objects have a natural frequency of vibration. Resonance occurs
when vibrations traveling through an object match the object’s natural
frequency.
• An object that is vibrating at its natural frequency absorbs energy from
the objects that vibrate at the same frequency. Occurs in music.