Properties of Waves

EQ: How do I describe the basic properties of waves and how a wave’s speed is related to its wavelength and

frequency?

Vocabulary

Crest - The highest point, or peak, of a wave.

Trough -The lowest point, or valley, of a wave.

Properties of Waves

• There are four wave properties– Amplitude– Wavelength– Frequency– Speed

water level at rest

fixed point

crest

trough

Frequency is the number of wavelengths passing a fixed point in a certain amount of

time, usually 1 second.

Wavelength is the distance from one crest or trough to the next.

Amplitude is the distance a medium moves

above or below its position at rest.

Means crest in a transverse wave

Means trough in a

transverse wave

Amplitude

The maximum distance that a disturbance causes a medium to move from its rest position; the distance between a crest or trough of a wave and line through the center of a wave.

Rope example: move your hand up and down at a greater distance, increases the amplitude. Uses more energy.

Slinky – high vibrations cause the compressions to be more crowded and rarefactions loose giving the slinky higher amplitude.

Which wave has a greater amplitude?

Which longitudinal wave has the larger amplitude?

Not very crowded

crowded

Wavelength

• The distance between two corresponding parts of a wave

Frequency• The number of complete waves that pass

a given point in a certain amount of time or the number of vibrations per second.

• Hertz (Hz) – measures frequency. A wave that occurs every second has a measurement of 1 Hz. If two waves pass you every second then the measurement is 2 Hz

• Example – if you move your hand slower, decreases frequency, move it faster increases frequency.

Speed

• Waves in different mediums travel at different speeds– Ex. Light and sound- see a flash of lighting,

hear a clap of thunder– Speed, wavelength and frequency related to

each other by the formula

Speed = wavelength x frequency

F = S W = S

W F

Go Figure

• The speed of a wave on a rope is 50 cm/s and its wavelength is 10 cm. What is the frequency?

• What is the speed of an object that travels 6 meters in 2 seconds?

• The speed of a wave on a guitar string is

100m/s and the frequency is 1000 Hz. What is the wavelength of the wave?

Class Work Homework

• Fill in– What did I learn– Confused– Say

– Read Section 1-2 in your textbook

Worksheet