PROPERTIES OF WAVES FREQUENCY & WAVE SPEED

REVIEW A wave is a disturbance that transfers energy from place to place. In science, energy is defined as the ability to do work. The disturbance caused by a wave is temporary. After the wave has passed, the medium returns to its original state.

REVIEW All vibrations produce waves. All waves transfer energy through vibrations. All waves propagate from a source. (They spread out in all directions.)

REVIEW Mechanical waves must have a medium to travel through. A medium is a solid, a liquid, or a gas. There are two types of mechanical waves, transverse or longitudinal.

REVIEW Transverse waves go up and down, at right angles to the movement of the energy.

REVIEW Longitudinal waves go back and forth, parallel to the movement of the energy.

REVIEW Electromagnetic waves transfer energy through empty space. Electromagnetic waves are always transverse waves.

REVIEW Longitudinal Wave compressionrarefaction wavelength amplitude

REVIEW crest trough amplitude rest line wavelength Transverse Wave Parts

WAVE PROPERTIES

INTRODUCTION All waves share certain properties. The basic properties of waves are: Amplitude Wavelength Frequency Speed

INTRODUCTION We will look at frequency and wave speed first. The frequency of a wave is the number of complete waves that pass a given point in a certain amount of time. If one wave passes that point every second, the frequency is one wave per second.

INTRODUCTION Frequency is measured in units called hertz (Hz). It was named for a German scientist named Heinrich Hertz, who first produced radio waves.

INTRODUCTION Frequency and wavelength are related to one another, because as one goes up the other goes down. As the wave moves faster and faster, its length gets shorter and shorter. As it slows down, its length gets longer and longer.

INTRODUCTION

So really long waves have low frequencies because they don’t repeat very often. They are too long to move fast. And really short waves have high frequencies because they move very fast past a given point.

INTRODUCTION

OBJECTIVES Name the basic properties of waves. Relate wave speed to wavelength and frequency.

VOCABULARY Frequency – how often something repeats itself.

IN QUESTION Label the parts of this longitudinal wave. Compression, rarefaction, wavelength, amplitude. compression wavelength amplitude rarefaction

FREQUENCY NOTES Frequency is measured in hertz (Hz). One hertz is one wave passing a point in 1 second. Hertz is named for Heinrich Hertz, a German scientist. As frequency goes up, wavelength goes down.

WAVE SPEED INTRO Imagine watching a distant thunderstorm approach on a hot day summer day. First you see a flash of lightning. A few seconds later you hear the thunder rumble. Even though the thunder occurs the instant the lightning flashes, the light and sound reach you seconds apart.

WAVE SPEED INTRO This happens because light waves travel much faster than sound waves. In fact, light waves travel about a million times faster than sound waves.

WAVE SPEED INTRO Different waves travel at different speeds. The speed of a wave is how far the wave travels in a given length of time, or its distance divided by the time it took to travel that distance. The speed, wavelength and frequency of a wave are related to one another.

WAVE SPEED INTRO The relationship between them can be shown by this formula: S = W x F Speed = Wavelength x Frequency

WAVE SPEED INTRO If the medium does not change, the speed of the wave will remain the same. For example, in air, at a given temperature and pressure, all sound waves will travel at the same speed. If temperature or pressure changes, then the speed of the sound wave will change.

WAVE SPEED NOTES Speed, wavelength and frequency are related to one another. Waves move at different speeds. Light waves move faster than sound waves.

WAVE SPEED NOTES Temperature and pressure can affect the speed of a wave. Formula to calculate for wavelength, speed, or frequency. S = speed F = frequency W = wavelength

OUT QUESTION Calculate the wavelength, in meters, of a wave that has a speed of 100 meters per second and a frequency of 10 hertz.