6 Waves Reload 1.1

Waves

Lesson 1.1: Understanding waves Lesson 1.2: Reflection of waves Lesson 1.3: Refraction of Waves Lesson 1.4: Diffraction Waves Lesson 1.5: Interference of Waves Lesson 1.6: Sound Waves Lesson 1.7: Electromagnetic Waves

1.1 Understanding Waves a) b) c) d) e) f) g) h)

Motion of waves Propagation of waves Type of waves Wavefronts Wave profile Graph= Displacement vs (distance)(time) Wave speed Damping and resonance

Waves 1.1 Understanding Waves

“An oscillating or vibrating motion in which a point or body moves back and forth along a line about a fixed central point produces waves” An oscillating or vibrating system acts as the source of waves which transfer energy from one point to another (without transferring matter)

A wave is a disturbance that transfers energy between two points through vibrations in a the two points medium, without transferring matter between the two points.

Examples of the waves: a) Light waves are produced as a result of vibrations of electrons in an atoms. b) Sound waves are produced by vibrating mechanical bodies such as guitar strings or a tuning fork. c) Water waves are produced by a disturbance (or vibration) on a still water surface.

Gelombang melintang Transverse Wave Dalam gelombang melintang, zarah zarah medium di anjakkan pada arah berserenjang dengan arah gerakkan gelombang.

A transverse wave is a wave in which particles of the medium move in a direction perpendicular to the direction which the wave moves.

Transverse waves on a string are another example. The string is displaced up and down as the wave travels from left to right, but the string itself does not experience any net motion.

Contoh gelombang membujur

Example of a longitudinal wave.

Penala bunyi yang bergetar memampatkan udara dalam paip pergi balik ke arah yang selari dengan arah pemindahan tenaga. Bunyi adalah gelombang membujur. A vibrating tuning fork will force air within a pipe to begin vibrating back and forth in a direction parallel to the energy transport; sound is a longitudinal wave

Have you ever "done the wave" as part of a large crowd at a football or baseball game? A group of people jumps up and sits back down, some nearby people see them and they jump up, some people further away follow suit and pretty soon you have a wave travelling around the stadium. The wave is the disturbance (people jumping up and sitting back down), and it travels around the stadium. However, none of the individual people the stadium are carried around with the wave as it travels - theyall remain at their seats.

Examples which illustrate the definition

Longitudinal sound waves in air behave in much the same way. As the wave passes through, the particles in the air oscillate back and forth about their equilibrium positions but it is the disturbance which travels, not the individual particles in the medium

Gelombang elektromagnetik adalah gelombang yang mampu memindahkan tenaganya menerusi vakum. Gelombang elektromagnetik di hasilkan oleh getaran elektron dalam atom di permukaan matahari.

An electromagnetic wave is a wave which is capable of transmitting its energy through a vacuum (i.e., empty space). Electromagnetic waves are produced by the vibration of electrons within atoms on the Sun's surface.

Wavefronts - is an imaginary line - A wavefront is a line that joints all the points vibrating in phase, such as a line passing through similar wave crests. - Points in a wave are in phase if they vibrate in the same direction with the same displacement.

When When aa wave wave is is present present in in aa medium medium (that (that is, is, when when there there is is aa disturbance disturbance moving moving through through aa medium), medium), the the individual individual particles particles of of the the medium medium are are only only temporarily temporarily displaced displaced from from their their rest rest position position MAIN MENU

WAVE FRONT WAVE FRONT

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Check your understanding 1) If the vibration of a wave are at right angles to the direction of the wave, it is called a _____________ wave. An example of this type of wave is ____________. 2) If the vibration of a wave are along the direction of the wave, it is called a ___________ wave. An example of this type of wave is _______________. 3) A wave carries energy from ____________ to _______________, without any transferring of the _________________.

• Equilibrium position is. • One complete oscillation has occurred when the bob has moved through positions A-B-C-BA, that is when it has returned to its starting position and is moving in the same direction. • Amplitude, a of an oscillation is the maximum displacement from the mean position. • Period, T of the oscillation is the time taken to complete one oscillation. • Frequency, f of the oscillation is the number of complete oscillation made in one second.

Oscillating System • Oscillating system consists of: – Amplitude – Period – Frequency – Wavelength – Wave speed

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Displacement – Time Graph s/cm

Peak

Amplitude, a t/s

Period

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Displacement – Distance Graph s/cm

Peak

Amplitude, a x/cm

Wavelength

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Frequency, f Numbers of oscillation in one second. Unit : Hertz (Hz) 1 f = T

C

A B

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Wave Speed, v • Wave speed, v depends on wavelength, λ and frequency, f. • Wave speed, v = λf

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• Wavelength, λ is the horizontal distance between two successive equivalent points on the wave. • Wave speed, v is the distance travelled by a wave in one second in the direction of propagation. • Wave speed, v is the distance moved by a crest in one second. • Wave speed , v = fλ

Check your understanding 1) The wavelength of a wave is the ______________ between two successive ______________ or ______________. 2) The frequency is the number of ________________ oscillations made in _____________ second. The unit for frequency is _______________. 3) The velocity of wave is equal to ______________ multiplied by _______________.

• The time taken for a vibrating system to make a complete oscillation is known as ______________. • The number of complete oscillation made by a vibrating system is known as ___________________. • The distance traveled by a wave in one second is known as ______________. • If the of an oscillating system is 0.2s and its wavelength is 60 cm, what is the velocity of the wave formed by this oscillating system?

Damping is said to have occurred in an oscillating system when the system loses energy to the surroundings, usually in the form of heat energy.