Review of Properties slides 2- 7 Wave Behaviors slides 11 - 28 MT 6 LT 2 Review of Properties slides 2- 7 Wave Behaviors slides 11 - 28 Waves

Review What is a wave? What is a medium? What are the 3 types of mediums? What is the difference between an electromagnetic and mechanical wave? What are the 3 types of Mechanical Waves?

Review A: What is a wave? A vibration that carries energy from one place to another A: What is a medium? The material through which waves travel through A: What are the 3 types of mediums? Solid, Liquid, Gas A: What is the difference between an electromagnetic and mechanical wave? Electromagnetic waves can travel through empty space (vacuum) & mechanical waves need a medium A: What are the 3 types of Mechanical Waves? Transverse, Longitudinal, and Surface

Review What is a transverse wave? What are the essential parts of a transverse wave?

Review What is a transverse wave? A transverse wave is where the medium moves perpendicular to the motion of the wave What are the essential parts of a transverse wave? Amplitude, wavelength, rest position, crest, trough

Review What is a longitudinal wave? What are the essential parts of a longitudinal wave?

Review What is a longitudinal wave? The motion of the medium vibrates in the same direction (parallel) as the wave travels. What are the essential parts of a longitudinal wave? Compression, Rarefaction, Wavelength

How do waves interact?

Through Wave Behaviors

Think, Write, Pair, Share What happens when… A wave meets a hard surface like a wall? A wave enters a new medium? A wave moves around an obstacle? A wave meets another wave?

Which Wave Behaviors will we focus on? 1. Refraction 2. Reflection 3. Diffraction 4. Interference 4a. Constructive 4b. Destructive 5. Doppler Effect 6. Polarization

1. What is Refraction? Why does it do this? The bending of a wave as it enters a new medium. Why does it do this? All waves change speed when they enter a new medium. Greater change in speed, more bending of wave!

Pencil: half in water, half in air and it looks bent Refraction - Example Video: Click Here Pencil: half in water, half in air and it looks bent

2. What is Reflection? When a wave hits a surface through which it cannot pass, it bounces back All types of waves can be reflected Light off a mirror Sound off a wall : Echo Show a rope tied to a chair or fixed object

Reflection - Example Image in clear water Video: Click Here Show a rope tied to a chair or fixed object

What is the difference between Reflection & Refraction? Reflection: the wave hits a barrier that it can’t pass through, so the wave bounces back Refraction: the wave bends as it continues into a new medium; speed also changes.

3. What is Diffraction? The bending of wave as it moves around a barrier or passes through a hole in a barrier. The larger the wavelength, the more it diffracts The wave will try to curve around the boundary or outward through the opening

Diffraction - Example Video: Click Here and Here Music around a corner of a building

4. What is Interference? The interaction of two or more waves There are two types: 4a. Constructive interference 4b. Destructive interference

4a. What is Constructive Interference? When crests of one wave overlap the crests of another wave to make a wave with a larger amplitude.

Constructive Interference - Example Click Here for video Example: You and another person each send a wave of equal frequencies from each end of a jump rope

4b. What is Destructive Interference? The crests of one wave overlap the troughs of another wave producing a smaller amplitude.

Destructive Interference - Example A muffler on a car cancels sound waves and makes it more quiet.

Learning Check 1. What is Refraction 2. What is Reflection? 3. What size wavelength will diffract more? 4. What is Constructive interference? 5. What is Destructive interference?

Learning Check 1. Refraction occurs when a wave enters a new medium at an angle because one side of a wave front moves more slowly than the other side. 2. Reflection is when a wave cannot pass through a barrier and bounces back. 3. The larger the wavelength is compared to the size of an opening or obstacle, the more a wave diffracts. 4. Constructive is when two waves combine and the amplitude increases Destructive is when two waves combine and the the amplitude decreases

5. What is the Doppler Effect? Change in pitch of a sound source as it passes you Pitch is high when it gets close to you Wavelength shorter, & frequency higher Pitch is lower as it passes you Wavelength longer, & frequency lower The pitch of the horn is high as it approaches and drops to a lower pitch as it passes you. It is important to appreciate that the actual frequency of the horn does not change. When the car approaches the wavelengths are shorter and when it recedes they are longer, causing the observer to hear first a higher pitch then a lower pitch. It’s important that students understand that the Doppler effect deals with pitch and not loudness. A very simple demonstration to illustrate the Doppler effect is shown on the right. Firmly tie a tuning fork to a strong string. Strike the fork and swing it in a circle as shown. The class should be able to hear the rise and fall in the pitch of the fork as it approaches and recedes from them.

Doppler Effect - Example Video: Click Here When a police car, w/sirens blaring, passes you traveling in the opposite direction at a high speed. The pitch of the horn is high as it approaches and drops to a lower pitch as it passes you. It is important to appreciate that the actual frequency of the horn does not change. When the car approaches the wavelengths are shorter and when it recedes they are longer, causing the observer to hear first a higher pitch then a lower pitch. It’s important that students understand that the Doppler effect deals with pitch and not loudness. A very simple demonstration to illustrate the Doppler effect is shown on the right. Firmly tie a tuning fork to a strong string. Strike the fork and swing it in a circle as shown. The class should be able to hear the rise and fall in the pitch of the fork as it approaches and recedes from them.

6. What is Polarization? ONLY with Transverse waves. Light that is passing through a special filter that blocks light waves that vibrate in certain directions. The light that is emitted by an incandescent light bulb is not polarized since the electromagnetic waves produced will be vibrating in random directions. However, using certain crystals, or by using a special plastic polarizing films, the transverse vibrations of a light source can be made to all vibrate in the same direction. (The fact that light can be polarized was the first proof that it was a transverse wave.) Radio, TV and even cell phone transmissions are produced by accelerating charges in a particular direction. For this reason, these electromagnetic waves are polarized. Light coming directly from the sun is not polarized, however, when the light interacts with the earth’s atmosphere, the light coming from the sky at right angles with the sun is highly polarized. (Photographers make use of this when photographing the sky to enhance the appearance of clouds.) When light reflects at an angle from a substance like water, it becomes polarized. This is why polarized sunglasses are so effective in reducing glare from horizontal surfaces.

Polarization - Example Video: Click Here Polarized Sunglasses The light that is emitted by an incandescent light bulb is not polarized since the electromagnetic waves produced will be vibrating in random directions. However, using certain crystals, or by using a special plastic polarizing films, the transverse vibrations of a light source can be made to all vibrate in the same direction. (The fact that light can be polarized was the first proof that it was a transverse wave.) Radio, TV and even cell phone transmissions are produced by accelerating charges in a particular direction. For this reason, these electromagnetic waves are polarized. Light coming directly from the sun is not polarized, however, when the light interacts with the earth’s atmosphere, the light coming from the sky at right angles with the sun is highly polarized. (Photographers make use of this when photographing the sky to enhance the appearance of clouds.) When light reflects at an angle from a substance like water, it becomes polarized. This is why polarized sunglasses are so effective in reducing glare from horizontal surfaces.