Part 1 – Wave Characteristics

What is a Wave?

• A disturbance that carries energy through matter or space.

What is a Wave?

2 Categories of Waves

• Mechanical Waves– Require a medium (material) to travel

through– Examples: water waves, sound waves

• Electromagnetic Waves– Do not require a medium– Example: light travels through empty

space

Wave Description

• Crest• Trough• Amplitude– Intensity of the wave.– How much energy is transferred.

• Wavelength– The distance from one point on

a wave to the same point on the next wave.

Wave Description

• Frequency• How frequently a wave pulse occurs.

– Unit• Hertz (Hz)• 1 Hz = 1/seconds or s-1

– Equation

𝒇=¿𝒘𝒂𝒗𝒆𝒔𝒕𝒊𝒎𝒆

Wave Description

• Period• The time (in seconds) that it takes for one

wave to pass.

– Equation

• T = Period (in seconds)

𝑻=𝒕𝒊𝒎𝒆

¿𝒘𝒂𝒗𝒆𝒔

Wave Description

• Frequency and Period are Inversely Related

𝑻=𝟏𝒇

𝒇=𝟏𝑻

Types of Waves

• Transverse Waves–Matter moves perpendicular to the

direction of wave movement.

Types of Waves

• Longitudinal Waves–Matter moves parallel to the direction of

wave movement.

Other Types of Waves!

• Surface (water) Waves

Wave Interactions

–When two (or more) waves are travelling through the same medium they will interact with each other.

– The net displacement is the sum of the two waves.

Wave Interactions

• Constructive Interference– The two waves are in-phase.– The Amplitudes add

together.

Wave Interactions

• Destructive Interference–Waves are out-of-phase.– Amplitudes “cancel out”

Wave Interactions

• Example:– Shown to the right are four different

pairs of wave pulses that move toward and interact with each other. Rank, from most to least, the height of the peak that results when the two pulses coincide.• Answer:

A,B,D,C

Standing Waves

• A repeated wave produces a pattern caused by the rotation of constructive and destructive interference.

Standing Waves

Wave Motion

• Waves transfer energy!• Matter has no net movement.

Wave Motion

• Waves transfer energy!• Matter has no net movement.

Wave Speed

• Equation

• Examples1. A wave with a wavelength of 2 meters

has a frequency of 50 Hertz. What is the velocity of the wave?• Answer: 100 m/s

𝒗= 𝒇 𝝀v = wave velocity (in m/s)f = frequency (in Hertz)λ = wavelength (in meters)

Wave Speed

• Examples2. Ocean waves are washing up on shore

with a velocity of 5 m/s. If they each have a length of 1.5 meters, what is the frequency of the ocean waves?• Answer: 3.33 Hz