Presentation on theme: "Waves & Energy Transfer Chapter 14. 14.1 Wave Properties Energy can be transferred by particles or by waves. Types of Waves - Mechanical, Electromagnetic,"— Presentation transcript:
Waves & Energy Transfer Chapter 14
14.1 Wave Properties Energy can be transferred by particles or by waves. Types of Waves - Mechanical, Electromagnetic, & Matter Mechanical waves require medium to travel, such as air, water, & springs or ropes.springs
EM waves do not require medium. Ex: light waves, radio waves & x- rays.light They all travel at speed of light (c). Matter waves involve electrons & other particles that demonstrate wave like properties under certain conditions.
Will be studied under Quantum Mechanics. Three types of mechanical waves. Transverse - particles vibrate perpendicularly to direction of motion of wave. Transverse vibrate Longitudinal - particles travel in direction of wave. Longitudinal Surface - mixture of transverse & longitudinal. Surface
Transverse waves do not travel through earths center, which indicates center is fluid. Wave pulse - a single disturbance travels through medium. Wave train or traveling wave - a series of pulses at regular interval.
Two Types of Waves
Measuring a Wave Period, - time required for motion to repeat itself. Frequency, f - number of complete vibrations per second. f = 1 / Wavelength, - distance from crest to crest or trough to trough. Wavelength
Crests - high points of wave Trough - low points of wave When time interval is one period, wave would move a distance of 1 wavelength. Velocity - given by v = / T or v = f Amplitude - maximum displacement from rest or equilibrium position.
Speed of sound in air depends on temperature. Speed of light is always constant. 3.00E8 m/s = c Ex. Prob 333 Prac Prob 335
14.2 Wave Behavior - Boundaries When wave reaches boundary of media, it may be reflected or pass. Speed & change when wave enters new medium. Fig Junction of two springs is a boundary between two media.
A pulse reaching boundary (a) is partially reflected & partially transmitted. (free)boundary free Fig A pulse is shown as it approaches a rigid wall (a) & as it is reflected from wall (b). Notice amplitude is almost same but reflected pulse is inverted.
When medium changes, wave energy is both reflected & transmitted. Waves passing from one medium to another have same f. The change depends on v change so that f = v/ is constant. Prac Prob 337
Wave Boundaries Less to MoreMore to less Less
Superposition of Waves Principle of superposition - displacement of a medium caused by two or more waves is algebraic sum of displacements caused by individual waves. Interference - result of superposition. Interference
Destructive interference occurs when crest meets trough. Destructive Resultant wave is smaller. Fig 14-11a a Constructive interference occurs when waves meet crest to crest or trough to trough. Constructive Resultant wave is larger. Fig b 338
If waves are opposite & equal magnitude, result is 0. Fig 14-11c 338 Continuous waves – from a region of higher speed to one with lower speed. Fig
Standing Waves Node - pt that is undisturbed. Node Medium is not displaced as waves pass. Antinode - pt of max displacement. Standing wave has stationary nodes & antinodes. Standing stationary It is result of identical waves traveling in opposite directions. Fig
Waves in Two Dimensions Law of reflection - angle at which a wave approaches a barrier is equal to angle at which it is reflected.reflection Fig Normal - to barrier. Angle of incidence - angle between incident ray & normal.
Angle of reflection - angle between normal & reflected ray. Refraction - change of wave direction at boundary between two media. Refraction Fig Diffraction bending of waves around barrier. Diffraction Fig & Fig
Bibliography dia/waves/em.html dia/waves/em.html /waves/u10l1c.html /waves/u10l1c.html wave01/Twave01Applet.html wave01/Twave01Applet.html /waves/u10l1c.html Physics: Principles and Problems, Glencoe Digital Curriculum