Ripple Tank SummaryRipple Tank Summary

Why Ripple Tanks :Why Ripple Tanks :

• Real waves (sound, light, radiation) Real waves (sound, light, radiation) are difficult to observeare difficult to observe

• Properties of waves should be Properties of waves should be independent of the type of waveindependent of the type of wave

• Water waves (which are easy to see) Water waves (which are easy to see) provide a useful analogy for other provide a useful analogy for other types of wavestypes of waves

Wave PropertiesWave Properties

• TransmissionTransmission

• ReflectionReflection

• RefractionRefraction

• DiffractionDiffraction

• InterferenceInterference

TransmissionTransmission

• The traveling of a wave through a The traveling of a wave through a medium away from a vibrating medium away from a vibrating sourcesource

TransmissionTransmission• The wavelength of the generated The wavelength of the generated

wave does not change as it travels wave does not change as it travels the length of the ripple tankthe length of the ripple tank

• The speed of the wave remains a The speed of the wave remains a constantconstant

TransmissionTransmission

• If the medium doesn’t change the If the medium doesn’t change the speed must remain constantspeed must remain constant

• A change in the frequency must A change in the frequency must result in a change in the wavelengthresult in a change in the wavelength

• An increase in the frequency causes An increase in the frequency causes a shortening of the wavelengtha shortening of the wavelength

ReflectionReflection

• The changing direction of a wave The changing direction of a wave upon impact with a barrier or objectupon impact with a barrier or object

ReflectionReflection

• The speed of the wave, frequency The speed of the wave, frequency and wavelength remains unchanged and wavelength remains unchanged after reflectionafter reflection

• Only the direction of the wave Only the direction of the wave changeschanges

ReflectionReflection

• The direction of the wave changes The direction of the wave changes such that the angle of incidence is such that the angle of incidence is equal to the angle of reflectionequal to the angle of reflection

RefractionRefraction

• Refraction is the bending of a wave Refraction is the bending of a wave as it passes from one type of as it passes from one type of medium into another type of mediummedium into another type of medium

RefractionRefraction

• As the surface waves travel from a As the surface waves travel from a deep to shallow environment the deep to shallow environment the waves will bend and decrease in waves will bend and decrease in wavelength.wavelength.

RefractionRefraction

• Since the frequency of the waves can Since the frequency of the waves can not change and the wavelength not change and the wavelength decreases, the speed of the wave as decreases, the speed of the wave as it travels from a deep section to a it travels from a deep section to a shallow section must decrease as shallow section must decrease as well. This causes the waves to “pile well. This causes the waves to “pile up” on one another.up” on one another.

• TsunamiTsunami

RefractionRefraction• This bending of the wave and the This bending of the wave and the

resultant change in speed has resultant change in speed has environmental implications!environmental implications!

DiffractionDiffraction• The bending of a wave as it either The bending of a wave as it either

passes by a barrier / object OR the passes by a barrier / object OR the spreading out of a wave as it passes spreading out of a wave as it passes through an openingthrough an opening

DiffractionDiffraction

• Longer wavelengths diffract easier Longer wavelengths diffract easier around a barrier compared to shorter around a barrier compared to shorter wavelengthswavelengths

• This is seen in the difference This is seen in the difference between light (a short wavelength) between light (a short wavelength) and sound (a long wavelength)and sound (a long wavelength)

DiffractionDiffraction• Waves can also diffract (bend) as Waves can also diffract (bend) as

they pass through an openingthey pass through an opening

• Maximum diffraction occurs when the Maximum diffraction occurs when the width of the slit is close to the width of the slit is close to the wavelength of the energywavelength of the energy

DiffractionDiffraction

• Diffraction is often used in creating Diffraction is often used in creating wave breaks to help dissipate the wave breaks to help dissipate the incoming energy of the waveincoming energy of the wave

InterferenceInterference

• The total disturbance within a The total disturbance within a medium when more than one wave is medium when more than one wave is presentpresent

InterferenceInterference• The amplitudes of the waves will add The amplitudes of the waves will add

together as vectors.together as vectors.

• A crest plus a crest forms a much A crest plus a crest forms a much larger crestlarger crest

• A trough plus a trough form a deeper A trough plus a trough form a deeper troughtrough

InterferenceInterference

• If a crest and crest (trough and If a crest and crest (trough and trough) add together we end up with trough) add together we end up with constructive interferenceconstructive interference

InterferenceInterference

• If a crest adds to a trough (or trough If a crest adds to a trough (or trough to a crest) we end up with to a crest) we end up with destructive interferencedestructive interference

InterferenceInterference

• In most cases we end up with partial In most cases we end up with partial interference creating a beat.interference creating a beat.

InterferenceInterference

• Many objects display an interference Many objects display an interference pattern (such as electrons)pattern (such as electrons)