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Home End HolisticTuition CashPlants Chapter 1: Waves Form 5 1 Physics Next > The study of matter.

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Presentation on theme: "Home End HolisticTuition CashPlants Chapter 1: Waves Form 5 1 Physics Next > The study of matter."— Presentation transcript:


2 Home End HolisticTuition CashPlants Chapter 1: Waves Form 5 1 Physics Next > The study of matter

3 Home End HolisticTuition CashPlants Objectives: (what you will learn) Objectives: (what you will learn) 1) understanding Waves 2) reflection of waves 3) refraction of waves 4) diffraction of waves 5) interference of waves 6) analysing sound waves 7)analysing electromagnetic waves Physics: Chapter 1 2 < Back Next >

4 Home End HolisticTuition CashPlants Understanding Waves: Physics 3 1.A wave is a traveling disturbance from a vibrating or oscillating source. < Back Next > 2.A wave carries energy along with it in the direction of its propagation. 3.A wave is a mean of energy transfer through vibration.

5 Home End HolisticTuition CashPlants Transverse Wave Transverse WaveWaves 4 Particles in the medium vibrate in a direction perpendicular to the direction of wave propagation. Perpendicular = 90 o to the line of direction. Examples: wave in a rope water waves light waves < Back Next >

6 Home End HolisticTuition CashPlants 5 < Back Next > Particles in the medium vibrate in a direction parallel (0 o to line of direction) to the direction of wave propagation. Examples: wave in a slinky spring sound wave Waves Longitudinal Wave Longitudinal Wave

7 Home End HolisticTuition CashPlants 6 < Back Next > Wavefront A surface on the wave where all particles vibrate in phase (coming together to the same level). Oscillations Vibration or oscillation of particles in a medium is like oscillation of simple pendulum or loaded spring. Waves Surface Waves Surface Waves This is both transverse waves & longitudinal waves mixed in one medium. Examples: earthquake or seismic wave shear wave in a slinky spring

8 Home End HolisticTuition CashPlants 7 < Back Next >Waves Complete Oscillation Complete cycle; e.g. motion from A to B & back to A. Amplitude, a Maximum displacement from equilibrium position that is halfway between crest (high) & trough (low). Period, T Time taken for a complete oscillation. Frequency, f Number of complete oscillation in one second; f = 1/T

9 Home End HolisticTuition CashPlants 8 < Back Next >Waves Speed of wave, v Distance traveled by wave per second, v = fλ Free Oscillation Occurs when a system oscillates without any external force acting on it. Natural Frequency, f n Frequency of a free oscillation. Simple pendulum l = length, g = gravity Loaded vertical spring m = mass, k = constant

10 Home End HolisticTuition CashPlants 9 < Back Next >Waves Damped Oscillation An oscillation whose amplitude decreases due to energy loss from the system (as heat to air resistance). Forced Oscillation An oscillation produced when a system is forced into oscillation by an external periodic force. Resonance Occurs when a system which is forced into oscillation oscillates with large amplitude; the condition being that the frequencies of both systems are equal to each other.

11 Home End HolisticTuition CashPlants 10 < Back Next > Reflection of Waves Angle of reflection = angle of incidence Reflected wave has same speed, frequency, & wavelength as the incident wave. λ λ ir v v Angle of reflection, r = Angle of incidence, i

12 Home End HolisticTuition CashPlants 11 < Back Next > Refraction of Waves Refraction of wave The change in velocity of wave when it travels from one medium to another. Water & light waves are refracted towards Normal when moving into shallower or denser region (frequency unchanged, speed & wavelength decrease), and away from Normal the other way round. But sound waves behave in the opposite way. (Try relate it to the resistances of medium)

13 Home End HolisticTuition CashPlants 12 < Back Next > Diffraction of Waves Diffraction Diffraction is the spreading of waves after passing a narrow slit or an obstacle. Waves are diffracted more if: Diffraction a.the slit is narrower b.the wavelength is longer Light has very short wavelengths, diffraction occurs only for slits with width of 10 -4 m or less. Sound has long wavelengths, diffraction of sound waves enable sound to go around corners.

14 Home End HolisticTuition CashPlants 13 < Back Next > Interference of Waves Principle of superposition of waves Displacement y, produced by 2 waves at a point is the vector sum of displacements y 1 & y 2 produced by each of the waves. y = y 1 + y 2 Interference = effect produced by superposition of waves from 2 coherent sources. Coherent sources = if they oscillate in phase, or antiphase, or with same phase difference & they have the same frequency.

15 Home End HolisticTuition CashPlants 14 < Back Next > Interference of Waves antinode: constructive superposition from 2 crests or troughs node: destructive superposition from crest & trough xa D Separation between 2 consecutive antinodal or nodal lines at distance D from the 2 sources: antinodal line nodal line λDλDλDλDa x = Young’s double-slit experiment

16 Home End HolisticTuition CashPlants 15 < Back Next > Sound Waves Sound waves are produced by vibrating sources. They are longitudinal waves requiring a medium for propagation. It cannot travel in vacuum. Applications of reflection of sound wave: a.sonar or high frequency sound waves used to determine depth of ocean b.Ultrasonography uses ultrasound waves to examine condition of fetus, the reflected waves used to form an image on a monitor. c.Ultrasound is also used to detect tumour in the body d.Reflection of ultrasound from rocks used in geological survey.

17 Home End HolisticTuition CashPlants 16 < Back Next > Electromagnetic Waves Common properties: a.Need no medium, can travel in vacuum. b.Travels at constant speed of light, c = 3 x 10 8 m s -1 in vacuum. c.Transverse waves. d.Wave properties like reflection, refraction, diffraction & interference. NameSourcesApplications Radio waves, microwavesInductor-capacitor circuitRadio, radar Infra-redHot objects, SunHeating, remote control, night vision Visible lightSun, lampsPhotography, fibre optics UltravioletVery hot bodies, Sun, tubesFluorescent lamp, sterilizer, sun bed X-raysX-ray tubeX-ray photography, radiotherapy, detection of cracks Gamma raysRadioactive nucleiRadiotherapy, sterilizer

18 Home End HolisticTuition CashPlants 17 Summary < Back What you have learned: 1.Understanding Waves 2.Reflection of waves Thank You 3.Refraction of waves 4.Diffraction of waves 5.Interference of waves 6.Sound & electromagnetic waves

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