1. Which part of the scientific
process does NOT have to be
accurate to be useful?
A. hypothesis
B. procedure
C. analysis
D. safe practices
2. Which of the following is NOT an
example of a hypothesis that can be
tested with an experiment?
A. Nonliving things do not grow and
develop.
B. Lipids do not mix with water.
C. Plant cells contain DNA.
D. Dogs are better than cats.
3. An experiment yields the three results
below, and each result differs from what the
hypothesis predicted. Which result(s) is (are)
still useful?
A. A solvent doesn’t break down a substance,
making it impossible to determine what elements
comprise it.
B. A mouse fed a tiny amount of food did not get
sick.
C. The amount of a substance revealed by an
experiment is double that which was predicted.
D. all of the above
4. An environmental scientist suspects that
acid precipitation is beginning to affect
certain lakes in Texas. What is the best way
to test this hypothesis? Why?
5. A newspaper headline says, “Detective
Has Theory on How Computers Were Stolen
from Warehouse.” Which of the following
words—hypothesis, law, fact, or
experiment—most accurately reflects the
use of the term THEORY in this newspaper
headline?
Let’s see what we
learned about wave
interactions
yesterday!
S8P5: Students will
explore the wave nature
of sound and
electromagnetic radiation.
a. Identify the characteristics of
electromagnetic and mechanical
waves.
d. Describe how the behavior of waves is
affected by medium (such as air, water,
solids).
e. Relate the properties of sound to
everyday experiences.
f. Diagram the parts of the wave and
explain how the parts are affected by
changes in amplitude and pitch.
What happens when a
wave runs into a different
medium or runs into
another wave?
What happens when a waves
encounters a boundary (a new
medium)?
1. Absorption
2. Reflection
3. Refraction
4. Diffraction
Energy in wave is
transformed into a
different form of
energy, usually
thermal energy.

The angle of incidence equals the angle of
reflection
◦ It bounces off at the same angle it hits the surface
with
45°
45°

a wave bending
◦ A wave moves from one medium (substance) into
another at an angle…
◦ it changes speed as it enters the second medium…
◦ which causes it to bend.

ex: water
Wave speed depends
on the medium
Click on picture for internet animation

A wave spreading
◦ A wave passes a barrier or moves through a hole in
a barrier…
◦ it bends and spreads out

ex: a harbor
when a wave bends around an edge
or spreads through an opening


familiar examples:
sound waves
(speakers in a room)
and water waves
(breaker opening in
harbors)
the amount of
diffraction increases
with increasing λ
when 2 or more waves meet while
traveling in the same medium
(overlapping waves)
 the NET displacement (amplitude) is the
sum of the amplitude of the waves
 Constructive or destructive interference
 Creates standing waves & beats


the result of two or more sound
waves overlapping


Waves combining
Constructive interference
◦ Waves add together to make a larger amplitude
+
+
=
=
larger displacement (larger amplitude)
crest overlaps crest 
or
tough overlaps trough
 Resonance
 When an object vibration at a particular frequency
 Seen in musical instruments, especially strings
 Sympathetic resonance
When one vibrating object induces a vibration in
another object
 Soldiers do not walk in
formation across bridges
 Tacoma Narrows Bridge

Destructive interference
◦ Waves add together to make a smaller amplitude
+
+
=
=
smaller displacement (smaller amplitude)
crest overlaps trough 
displacement/
amplitude is reduced
crest cancels trough 
Different sounds that you hear include
(A) noise, (B) pure tones, and (C)
musical notes.
Overlapping waves of different f
(frequencies)

In music interference creates “beats”
(changes in loudness & softness)
Wave 1 (red) and
Wave 2 (blue)
combine to form beat pattern (in
green)
High amplitude = LOUD
Low amplitude = soft
Student #1: Fan the cards
Student #2: Pick a card and asks the
question
Student #3: Answers the question
Student #4: Praise if correct or tutors if
wrong







What creates sound
Sound wave type
Loudness (volume) related to amplitude
Frequency related pitch
Wavelength vs. frequency and pitch
Music and Noise
Wave interactions
 Absorption
 Reflection (if its sound, its an echo)
 Refraction
 Diffraction
 Interference
 Constructive Interference
 Destructive Interference
Change in frequency (and pitch) due to
a moving sound source is known as the
Doppler effect.
http://www.kettering.edu/~drussell/Demos/doppler/carhorn.wav
http://sol.sci.uop.edu/~jfalward/wavessound/wavessound.html
http://www.fearofphysics.com/
Objects moving towards you -- increase
in frequency or pitch (pitch rises)
Objects moving away from you -decrease in frequency or pitch (pitches
sinks)