Topic 5Waves

I. What are waves?

A. Disturbance that transmits energy through matter or space.

B. Waves carry energy.

C. The material does not move with the energy. Ex. Phone rings you don’t feel a rush of air.

II. Types of Waves

A. Mechanical Wave is a wave that requires a medium. Medium= substance through which waves travel. Ex. If in a vacuum no sound will be heard.

1. Examples

a. Sound waves

b. Ocean waves

c. Guitar String

B. Electromagnetic Waves are waves that do not “require” a medium but can travel through one. Ex. Sunlight traveling through air and water. Fastest when no medium.

1. Examples

a. Light Waves

b. X-Rays

c. Microwaves

C. Transverse particles vibrate with an up and down motion.

1. Examples

a. Electromagnetic waves

b. Wave on a rope

2. Parts of a transverse wave

a. Crest- highest point

b. Trough- lowest point

3. Picture of a Transverse wave

D. Longitudinal wave particles of the medium vibrate back and forth along the path that the waves travel. Ex. Slinky.

1. Example

a. Sound waves

2. Types of Movement in a Longitudinal wave

a. Rarefaction- particles less crowded.

b. Compression- particles are crowded.

3. Picture of a Longitudinal Wave

E. Surface Waves – combination of transverse and longitudinal waves between two media (air and water)

III. Properties of Waves

A. Amplitude maximum position the wave vibrates from its rest position. Height of the wave.

1. Larger amplitude = taller wave.

2. Larger amplitude = more energy.

B. Wavelength is the distance between any 2 adjacent crests or compressions in a series of waves or troughs and rarefactions.

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

1. Higher frequency = more energy.

D. Wave Speed is the speed at which a wave travels (distance traveled over time). Depends greatly on medium. Ex. Speed sound in air= 340 m/s in steel=5,200 m/s.

E. Calculating Wave Speed, Wavelength, Frequency

1. Formula V= λ x f (λ= lambda)

2. Sample Problem

What is the speed of a wave that has a wavelength of 4m and a frequency of 8hz?

V= 4 x 8 V=32m/s

IV. Wave Interactions

A. Reflection occurs when a wave bounces back after striking a barrier. Ex. Water, sound=echoes, sunlight on moon.

B. Refraction is the bending of a wave as it passes at an angle from one medium to another. Ex. Pencil in water.

C. Diffraction is the bending of waves around a barrier or through an opening. Ex. Sound around a corner.

D. Interference is the result of 2 or more waves overlapping.

1. Constructive crests of 1 wave overlaps the crest of another wave. Increase amplitude.

2. Destructive crests of 1 wave overlaps the trough of another. Decrease amplitude.