Presentation on theme: "Waves Energy can be transported by transfer of matter. For example by a thrown object. Energy can also be transported by wave motion without the transfer."— Presentation transcript:
1 WavesEnergy can be transported by transfer of matter. For example by a thrown object.Energy can also be transported by wave motion without the transfer of matter. For example by sound waves and electromagnetic waves.
2 WavesMechanical waves travel through matter. The matter is referred to as a “medium”. Examples are sound eaves, waves on a string, and waves on water.Electromagnetic waves do not require a medium through which to travel. Examples are gamma rays, x-rays, ultraviolet light visible light etc.
3 WavesA wave is a disturbance or oscillation that travels through matter or space, accompanied by a transfer of energy.
4 WavesA transverse wave causes the medium particles to vibrate in the direction perpendicular to the motion of the wave.
5 WavesA longitudinal wave causes the medium particles to vibrate in the direction parallel to the motion of the wave.
6 WavesA pulse is a single disturbance travelling through a medium or space.
16 WavesA standing wave oscillates with time but appears to be fixed in its location
17 Figure Wave superposition occurs when two or more waves meet in the same medium. The principle of superposition states that at the point where two or more waves meet the displacement of the medium equals the sum of the displacements of the individual waves.
18 Figure 14-20 The effect of two or more waves travelling through a medium is called interference. Constructive interferenceDestructive interference
19 Figure 14-20 Nodes and antinodes Nodes occur at points where two waves interact in such a way that the medium remains undisturbed.Antinodes occur at points where two waves interact in such a way that maximum displacement of the medium occurs.
21 Figure 14-20 Nodes and antinodes If one end of a string is attached to a vibrating object, and the other end is fixed, two wave trains are produced. One by the incident vibration, and one by reflection from the fixed end. The reflected wave train returns to the source and is reflected again. If the second reflection is in phase with the source, constructive and destructive interference will produce stationary antinodes and nodes. The string will appear to be vibrating in segments.
22 Figure 14-20 Nodes and antinodes This is called a standing wave an is an example of resonance.
26 Reflection of WavesWhen a wave train strikes a barrier it is reflected.The law of reflection states that the angle of incidence is equal to the angle of reflection.The direction of the wave train’s travel is called a ray, and the angles are measured from the normal to the boundary.
28 Refraction of WavesWhen a wave train moves from one medium to another, its velocity changes.Since the waves in the new medium are produced by the waves in the old medium, their frequency remains the same. Since the velocity changes, but not the frequency, the wavelength must change.
29 Refraction of WavesWhen parallel waves approach a boundary between media along the normal, their direction does not change.When parallel waves approach a boundary between media at an angle to the normal, their direction is changed. This phenomenon is called refraction.
30 Refraction of WavesWhen parallel waves approach a boundary between media along the normal, their direction does not change.When parallel waves approach a boundary between media at an angle to the normal, their direction is changed. This phenomenon is called refraction.
36 Diffraction of WavesAn interference pattern can be created by placing a barrier with two openings in front of a wave train.The openings must be smaller than the wavelength of the approaching wave train.
38 Diffraction of WavesIn regions where crests overlap with crests, and troughs overlap with troughs, constructive interference occurs, and antinodes lie along those lines. These lines are called antinodal lines.In regions where crests overlap with troughs destructive interference occurs, and the medium is undisturbed. These lines are called nodal lines.
39 Diffraction of WavesThe pattern produced is called an interference pattern.Different wavelengths produce similar interference patterns, but the nodal and antinodal lines are in different places.Regardless of wavelength a central antinodal line always falls in the center of the pattern.
40 Standing waves on a string – In order for standing waves to form on a string, the length of the string L must be a multiple of one half the wavelength