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)? 3. Refraction 1. Absorption 2. Reflection 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°

 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

 familiar examples: sound waves (speakers in a room) and water waves (breaker opening in harbors)  the amount of diffraction increases with increasing λ when a wave bends around an edge or spreads through an opening

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 Tacoma Narrows Bridge

 Destructive interference ◦ Waves add together to make a smaller amplitude += + =

smaller displacement (smaller amplitude) crest cancels trough  crest overlaps trough  displacement/ amplitude is reduced

Different sounds that you hear include (A) noise, (B) pure tones, and (C) musical notes.

 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 Overlapping waves of different f (frequencies)

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

Objects moving towards you -- increase in frequency or pitch (pitch rises) Objects moving away from you -- decrease in frequency or pitch (pitches sinks)