WAVES  Komang Gde Suastika  Physics Dept  Palangka Raya University 

What do you know? About waves?

 Tujuan 1. By the end of this lesson you will be able to: State that a wave transfers energy. 2. Use the following terms correctly in context: wave, frequency, wavelength, speed, amplitude, period. 3. State the difference between a Mechanical Waves and a Electromagnetic waves (EM Waves), and give an example of each. 4. State the difference between a longitudinal wave and a transverse wave, and give an example of each.

Perhatikan Fenomena berikut

WAVES a disturbance that transfers energy

Waves transfer energy…

CHARACTERISTICS OF WAVES Waves are described according to their  Amplitude measures DISPLACEMENT size of the disturbance  Wavelength distance of a “repeating unit” Also called a cycle  Velocity v speed = how fast wave travels

AMPLITUDE Distance between “rest & crest” or “rest & trough” Distance between “rest & crest” or “rest & trough” Gives indication of “power” or “strength” of wave (magnitude of earthquake = Richter scale) Gives indication of “power” or “strength” of wave (magnitude of earthquake = Richter scale) Does not affect velocity of wave Does not affect velocity of wave Determines loudness (sound) or brightness (EM wave) Determines loudness (sound) or brightness (EM wave)

WAVELENGTH WAVELENGTH  Distance between any two repeating points on a wave crest-crest, trough-trough, expansion-expansion, compression-compression  Determines what colors we see; what notes we hear (pitch)  Shorter wavelengths have more cycles per minute because they aren’t as long

VELOCITY v  the rate at which the energy travels; speed & direction  Depends on medium Mechanical waves travel faster through dense mediums Mechanical waves travel faster through dense mediums EM Waves are faster through less dense mediums EM Waves are faster through less dense mediums

Frequency ƒ  measured in wavelengths/second or cycles/second Hertz (Hz) = number of wavelengths in 1 second  Frequency is related to velocity: v = ƒ  Frequency is related to velocity: v = ƒ  How often number of wavelengths that pass any point per second

PERIOD T  How long Amount of time for one wavelength to pass a point  Related inversely to frequency 1 = 1 Tf Period = 1 Frequency

Properties of Waves  What is meant by the axis of a wave? The axis is the line running through the middle of the wave pattern.

What is meant by the crest of the wave? The crest is the top part of the wave

…and the trough? The trough is the bottom part of the wave.

What is the amplitude of the wave? The amplitude is the distance from the axis to the crest

or from axis to trough.

Definition of Wavelength? The wavelength is the distance after which the wave pattern repeats itself – the distance between two identical points on the wave

Wavelength is given the symbol λ pronounced lambda.

Frequency  The frequency of the wave is the number  of waves each second.  It is measured in hertz (Hz) which just  means “per second”.

Frequency  Calculate the frequency of each of the following waves: following waves:  125 waves passing a point in 10 seconds.  16 waves passing a point in 24 seconds.  30 waves passing a point in 1 minute.

 Carries energy from one place to another  Classified by what they move through 1. Mechanical Waves the energy is transferred by vibrations of medium (medium = matter) ex/ ocean waves move through water 2. Electromagnetic waves (EM Waves) the energy moves through disturbances in the electromagnetic field.

WAVE STRUCTURE CREST (peak) AMPLITUDE resting to max peak WAVELENGTH TROUGH

MECHANICAL WAVES travel through & gradually lose energy to that medium  Examples: water, sound, rope, & spring waves water, sound, rope, & spring waves  Mechanical Media: water, air, rope, spring water, air, rope, spring require a medium ( the material through which the disturbance is moving) to transmit energy Making a pulse

MECHANICAL WAVES Classified by how medium vibrates Pulse = direction of energy transfer Vibration = direction of vibration of medium relative to pulse 3 typestypes: Longitudinal,transverse,surface

MECHANICAL WAVES Classified by how medium vibrates Longitudinal Waves: Vibration is in the same direction as wave pulse (parallel to wave pulse) Transverse Waves: Vibration is at 90 0 (right angles) to wave pulse Surface Waves: Vibration is circular Ex/ Ocean waves; surface waves

TRANVERSE WAVES  Sideways or up & down  Examples: S-type earthquake waves S-type earthquake waves Electromagnetic (EM) or light waves Electromagnetic (EM) or light waves Vibration is perpendicular to the direction of the motion of the wave

LONGITUDINAL WAVES  Back and forth (compression & rarefraction)  Also called compression or pressure wave  Examples: P-type earthquake waves P-type earthquake waves Sound waves Sound waves Vibration is parallel to the direction of the motion of the wave Rarefraction (expansion) Compression

Waves describe the Earth S waves move through solids only!!! P waves move through solids & liquids Are these MECHANICAL WAVES???? YES!! Seismic waves need a medium (the earth!)

Penjalaran Gelombang dalam Satu Dimensi Fungsi Gelombang : Menjalar ke kanan Menjalar ke kiri Cepat-rambat Gelombang (Kecepatan Fasa) :

Superposisi dan Interferensi Gelombang

Gelombang Bunyi

Cepat-rambat Gelombang di dalam Dawai Tegangan dawai Massa dawai persatuan panjang Refleksi dan Transmisi Gelombang

Rambatan gelombang dari medium kurang rapat ke medium yang lebih rapat Rambatan gelombang dari medium lebih rapat ke medium yang kurang rapat

Harmoni Gelombang A

Untuk Gelombang yang Menjalar ke kanan atau

 PERSAMAAN GELOMBANG x x  f (x)t = 0  c t f (x - ct)

 Gelombang Sinusoidal Dalam Domain Ruang Amplitudo x  A Panjang gelombang Bilangan gelombang x

 Gelombang Sinusoidal Dalam Domain Waktu t  A T Perioda Amplitudo Frekuensi sudut Frekuensi

 Dalam Domain Ruang Dan Waktu

Sebuah gelombang perpindahan dinyatakan dengan :  (x,t) = 0,02 sin [ 2  ( 0,5 x – 10 t ) ] m Tentukan panjang gelombang, frekuensi dan kecepatannya.  Contoh

Jawab :

Tugas Tugas  Persamaan suatu gelombang yang bergerak transversal Dimana x dan y dalam cm dan t dalam detik. Berapa amplitudo, panjang gelombang, frekuensi dan kecepatan rambat gelombang itu