Chapter 15 Section 3

Chapter 15 Section 3

Waves behave in predictable ways

Waves interact with materials.

Waves behave predictably when they interact with barriers or other obstacles. Waves can undergo reflection, refraction, or diffraction.

Reflection

In reflection, waves meet a solid barrier and bounce back. For example, an echo occurs when a sound wave meets a wall and bounces back to the source of the sound.

Refraction

In refraction, waves move from one medium to another and bend, or refract. An example is a glass of water with a straw. Where the straw passes into the water, it looks broken. But the break is an illusion caused by refraction of light waves as they pass from air to water.

Diffraction

In diffraction, waves interact with a partial barrier and a portion of the waves pass through and spread out. An example is the way sound waves spread around corners.

Waves interact with other waves.

constructive and destructive interference

Constructive Interference

In constructive interference, two waves combine in phase, so that a crest meets a crest or a trough meets a trough.

Destructive Interference

In destructive interference, two waves of the same frequency meet up such that the trough of one wave joins with the crests of the other. If the amplitudes of the two original waves are equal, the two waves cancel each other out.

Multiple Choice

Explain what happens when waves encounter a medium that they cannot travel through.

• waves reflect

• waves absorb

• waves refract

• waves diffract

Multiple Choice

Describe a situation in which waves would diffract.

• light waves hit a mirror

• ocean waves hit a spot of land

• sound waves hit a wall

Multiple Choice

Describe two ways that waves are affected by interference.

• they cancel each other out

• amplitudes can add up

• amplitudes can add up or cancel each other out.

Multiple Choice

Explain how reflection and diffraction can happen at the same time in a wave.

• When a wave hits a partial barrier, the part of the wave that hits the barrier reflects in the oncoming waves. The part of the wave that passes through the gap in the barrier diffracts.

• When a wave hits a partial barrier, the part of the wave that hits the barrier diffracts in the oncoming waves. The part of the wave that passes through the gap in the barrier reflects.

Multiple Choice

How is interference similar to net force? How do you think the two concepts are related? HINT: Think about how forces are involved in wave motion.

• Interferences are responsible for moving a wave medium up and down as a wave passes through it. Forces can be added or subtracted on a wave medium just as they can on any object.

• Forces are responsible for moving a wave medium up and down as a wave passes through it. Forces can be added or subtracted on a wave medium just as they can on any object.