Objectives Identify how waves transfer energy without transferring matter. Contrast transverse and longitudinal waves. Relate wave speed, wavelength, and frequency. Relate a wave’s speed to the medium in which the wave travels. Describe how waves are reflected and explain how waves diffract. Apply the principle of superposition to the phenomenon of interference.

Waves and Energy Transfer Chapter 14 Waves and Energy Transfer

Sec. 1 Wave Properties Mechanical wave Transverse waves – waves that vibrates perpendicular to the direction of motion. Longitudinal waves – wave disturbance that moves in the same direction as, or parallel to, the direction of wave motion. Surface waves – have characteristics of both transverse and longitudinal waves.

Measuring a Wave Speed and amplitude Wavelength Period and frequency v = Δd / Δt Amplitude depends on how the wave is generated not on the speed of the wave. Wavelength Measuring a wave from one trough to the next or one crest to the next will give you the wavelength. Period and frequency The frequency of a wave, f, is the number of complete oscillations it makes each second. The period, T, is the time it take to make one oscillation.

Equations f = 1 / T v = λ f v = Δd / Δt

Sec. 2 Wave Behavior Waves at Boundaries When a wave moves from one medium to another, some of the energy is transmitted while some of it is reflected. Whether the reflected wave is inverted or not depends on the medium properties of both. When a wave hits a rigid boundary, the reflected wave will be inverted.

Superposition of Waves The displacement of a medium caused by two or more waves is the algebraic sum of the displacements caused by the individual waves. This is know as the principle of superposition. The result of the superposition of two or more waves is called interference.

Wave Interference Wave interference can be either constructive or destructive. Destructive interference – produces a node Constructive interference – produces an antinode A node is a point which does not move at all. An antinode is a point where the greatest displacement occurs when two waves combine. Waves can be of any shape or size. Continuous waves Recall that the velocity of a wave is the product of wavelength and frequency. Standing waves

Waves in Two Dimensions Ray diagrams will be used to model the movement of waves in two dimensions Reflection of waves in two dimensions – The angle of reflection is equal to the angle of incident and both are measured between the ray and the normal to the barrier. This is know as the law of reflection. Refraction of waves – the change in direction of a wave at the boundary between two different media.

Diffraction and Interference of Waves The spreading of waves around an edge of a barrier is called diffraction. If a barrier has two closely spaced holes, the waves are diffracted by each hole. These two waves interfere with each other and form regions of both constructive and destructive interference (nodes and antinodes).

In Summary: How do waves transfer energy? Contrast transverse and longitudinal waves. What is the relationship between wave speed, wavelength, frequency, and period? How does the medium affect wave speed? What is the difference between reflection and refraction? What is wave interference and how does it occur?