17.3 Behavior of Waves

17.3 Key Concepts

• How does reflection change a

wave?

• What causes the refraction of a

wave when it enters a new medium?

• What factors affect the amount of diffraction of a

wave?

• What are two types of interference?

• What wavelengths will produce a standing wave?

17.3 Behavior of Waves

The ripples visible on the bottom of the pool are caused by light shining through ____________ waves.

surface

17.3 Behavior of Waves

Reflection occurs when a wave ____________ off a surface that it cannot pass through. • Ex: When waves bounce of the side of a pool

________

Reflection

Reflection does not change the speed or frequency of a wave, but the wave can be flipped ______________.

bounces

wall

upside down

17.3 Behavior of Waves

Refraction is the _____________ of a wave as it enters a _____ _____________ at an ____________.

Refraction

When a wave enters a medium at an angle, refraction occurs because ____________ of the wave moves more ______________ than the other side.

bendingnew medium

angle

one side

slowly

17.3 Behavior of Waves

Ex: Think of a lawnmower when it is pushed at an angle from the grass onto the gravel.

The wheel on the _____________ slows down, but the other wheel is still moving at a faster speed on the grass.

Refraction Grass Gravel

Left wheel is still rolling faster on grass.

Direction changes.

Mower pivots because the right wheel moves more slowly when it reaches gravel.

gravel

17.3 Behavior of Waves

An ocean wave bends or ____________ as it approaches the shoreline.

The __________ water can be considered a new medium

Refraction

refracts

shallow

17.3 Behavior of Waves

The ________ side of the wave reaches the shallow water first and _______ down, causing the wave to bend

If a wave front approaches a shoreline perfectly ______________, no refraction occurs

Refraction

left

slows

parallel

17.3 Behavior of Waves

Diffraction is the bending of a wave as it moves _____________ an obstacle or passes through a ________________ opening.

Diffraction

A wave diffracts more if its wavelength is _______________ compared to the ________ of an opening or obstacle.

around

narrow

large size

17.3 Behavior of Waves

A. This wave diffracts, or _______________, after it passes through a narrow opening.

B. Diffraction also occurs when a wave encounters an __________________.

Diffraction

spreads out

obstacle

17.3 Behavior of Waves

Interference occurs when two or more waves ________________ and combine together.

Interference

Two types of interference are _______________ interference and _______________ interference.

overlap

constructivedestructive

17.3 Behavior of Waves

When waves collide, they can occupy the same region of space and then continue on.

• Constructive interference occurs when two or more waves combine to produce a wave with a _____________ displacement.

• Destructive interference occurs when two or more waves combine to produce a wave with a _________________ displacement.

Interference

larger

smaller

17.3 Behavior of Waves

Constructive Interference

Two waves with equal frequencies travel in opposite directions.

When a _________ meets a ______________, the result is a wave with an increased amplitude.

Interference

crest

crest

17.3 Behavior of Waves

Destructive Interference

Two waves with equal frequencies travel in opposite directions.

When a ___________ meets a ____________, the result is a wave with a reduced amplitude.

Interference

crest

trough

17.3 Behavior of Waves

A standing wave is a wave that appears to stay in ________________— it does not seem to move through the medium.

Ex: Think of plucking a guitar

string

Standing Waves

A standing wave forms only if _________ a wavelength or a _______________ of half a wavelength fits exactly into the _____________ of a vibrating cord.

one place

halfmultiple

length

17.3 Behavior of Waves

Interference occurs as the _____________ waves pass through the ______________ waves.

What would cause an

incoming wave on a guitar

string?

And a reflected wave?

Standing Waves

incoming

reflected

plucking a string

wave bouncing off ends

17.3 Behavior of Waves

A ___________ is a point on a standing wave that has no displacement from the rest position.

At the nodes, there is complete ______________ interference between the incoming and reflected waves.

An ______________ is a point where a crest or trough occurs midway between two nodes.

Standing Waves

node

destructive

antinode

17.3 Behavior of Waves

These photos show standing waves for two different frequencies.

A. ________ wavelength equals the length of the cord.

B. ________ wavelengths equal the length of the cord.

Standing Waves

One

Two

17.3 Behavior of Waves

Assessment Questions

1. The property of waves bending as they pass through a narrow opening is called a. reflection.

b. refraction.

c. diffraction.

d. destructive interference.

17.3 Behavior of Waves

Assessment Questions

2. When does refraction of a wave occur? a. The wave cannot enter the new medium.b. The wave enters a new medium at an angle.c. The wave enters a new medium at a parallel position.d. Part of the wave enters a new medium and part is

reflected.

17.3 Behavior of Waves

Assessment Questions

3. A 6-meter rope is tied to a hook in the wall. Which of the following wavelengths can produce a standing wave? a. 1.5 m

b. 2.5 m

c. 3.5 m

d. 4.5 m

17.3 Behavior of Waves

Assessment Questions

4. The amount of diffraction of a wave increases as the size of the obstacle causing the diffraction decreases.

TrueFalse