Section 1 The Nature of Waves Wave lany

Section 1 The Nature of Waves

Wave lany disturbance or movement that transmits energy through matter or space l. Waves carry energy without transporting matter.

l. All waves are produced by something that vibrates. l. Medium—a material through which a wave travels. ¡solid, liquid, or gas ¡Not all waves need a medium Ex: Electromagnetic waves

Types of Waves ¡ 3 kinds: l. Transverse l. Longitudinal l. Surface

¡Transverse waves—waves in which the particles vibrate with an up-and-down motion. animation

¡Longitudinal waves—the particles in the medium vibrate back and forth along the path that the wave travels. animation

¡Surface waves- when a transverse and longitudinal wave combine. ¡Example: ocean waves

Section 2: Properties of Waves

Ways waves differ l. How much energy they carry l. How fast they travel l. How they look

n l. Wavelength—the distance between any two adjacent crests or compressions in a series of waves.

l. Transverse waves have crests— the highest points, and troughs— the lowest points.

l. Longitudinal waves have dense regions called compressions and less dense regions called rarefactions.

Wavelength l Distance between one point on a wave and the nearest point just like it ¡Ex. crest to crest or trough to trough, compression to compression, rarefaction to rarefaction

l. Amplitude—the maximum distance the wave vibrates from its rest position. l. The more energy a wave carries, the greater its amplitude.

Amplitude of longitudinal waves ldenser compressions = larger amplitude = more energy the wave carries lless dense rarefactions = larger amplitude = more energy the wave carries A B

Amplitude of transverse waves l. The distance from the crest or trough of a wave to the normal position of the medium

• Frequency—the number of waves produced in a given amount of time. Expressed in hertz (Hz)

Higher frequency means more energy. As frequency increases, wavelength decreases.

Wave Speed l. Wave speed is the speed at which a wave travels. l. Wave speed (velocity) = wavelength x frequency

l. Light waves travel faster than sound waves. l. Sound waves travel faster in liquids and solids than in gas. l. Light waves travel faster in gases and empty space than in liquids and solids.

DISCUSSION QUESTION: l. In a thunderstorm, why do you see the lightning before you hear the thunder? l. Light waves travel much faster than sound waves.

Section 3: Wave Interactions l. Reflection occurs when a wave strikes an object and bounces off of it. l. All types of waves can be reflected.

l. Refraction—the bending of a wave caused by a change in its speed as it moves from one medium to another lgreater change in speed = more the wave bends.

lwave passes into a material that slows it down, it is bent toward the normal lwave passes into a material that speeds it up, it is bent away from the normal.

l. Diffraction—an object causes a wave to change direction and bend around it

l. If obstacle < wavelength, wave diffracts a lot. l. If obstacle > than the wavelength, wave does not diffract much. l. The larger the obstacle is compared to the wavelength, the less the waves will diffract.

l. Interference— two or more waves combine, form a new wave l. Waves pass through each other, continue in their original direction l. New wave exists only while the original waves continue to overlap.

l. Constructive interference— waves add together

Constructive Interference

l. Destructive interference— waves subtract from each other l D. I.

Destructive Interference

l. Standing waves—a wave pattern that stays in one place l. Form when waves of = wavelength and amplitude traveling in opposite directions continuously interfere with each other. l. Nodes—the places where two waves always cancel each other

l. Resonance—the ability of an object to vibrate by absorbing energy at its natural frequency