Each point on the wave front emits a semicircular wave that moves at the propagation speed v. A wave front is the long edge that moves, for example, with the crest or the trough. The new wave front is tangent to all of the wavelets.įigure 1.26 shows how Huygens’s principle is applied. Starting from some known position, Huygens’s principle states that every point on a wave front is a source of wavelets that spread out in the forward direction at the same speed as the wave itself. The Dutch scientist Christiaan Huygens (1629–1695) developed a useful technique for determining in detail how and where waves propagate. The direction of propagation is perpendicular to the wave fronts (or wave crests) and is represented by a ray. The view from above is perhaps more useful in developing concepts about wave optics.įigure 1.25 A transverse wave, such as an electromagnetic light wave, as viewed from above and from the side. The side view would be a graph of the electric or magnetic field. From above, we view the wave fronts (or wave crests) as if we were looking down on ocean waves. A light wave can be imagined to propagate like this, although we do not actually see it wiggling through space. Huygens’s principle is an indispensable tool for this analysis.įigure 1.25 shows how a transverse wave looks as viewed from above and from the side. This is particularly true when the wavelength is not negligible compared to the dimensions of an optical device, such as a slit in the case of diffraction. However, some phenomena require analysis and explanations based on the wave characteristics of light. So far in this chapter, we have been discussing optical phenomena using the ray model of light. Use Huygens’s principle to explain diffraction.Use Huygens’s principle to explain the law of refraction.Use Huygens’s principle to explain the law of reflection.The following two videos cover the features of sound as they propagate into a different medium, alongside other sound waves or around corners.By the end of this section, you will be able to: Wave superposition occurs when two or more sound waves are travelling through the same medium at the same time, the net displacement at any point in time, is simply the sum of the individual wave displacements. R esonance is the tendency of a system to vibrate with increasing amplitudes at unique frequencies of excitation. Diffraction is the bending of sounds waves around obstacles and openings. Reflection of sound waves occurs when it strikes the surface of another medium and bounces back in some other direction, causing echoes more than 0.1 seconds after the original sound wave was heard. In this post, we conduct investigations to analyse the reflection, diffraction, resonance and superposition of sound waves, as a part of the Prelim Physics course under the module Waves and Thermodynamics and sub-part Sound Waves. What is reflection, diffraction, resonance and superposition in term of sound waves? Latent Heat Involved in a Change of State.Relationship between the Change in Temperature of an Object and its Specific Heat Capacity (Q = mc△T).Relationship Between the Temperature of an Object and Kinetic Energy.Applying Equations and Relationships to Solve Questions (Refraction Index, Snell's Law, Critical Angle, Intensity of Light).Relationship Between the Inverse Square Law, the Intensity of Light and the Transfer of Energy.Practical Investigation: Phenomenon of the Dispersion of Light.Refraction and Total Internal Reflection.Practical Investigation: Formation of Images in Mirrors and Lenses.Behaviour of Standing Waves on Strings and Pipes.Reflection, Diffraction, Resonance and Superposition of Sound Waves.Relationship Between Distance and Intensity of Sound.Displacement of Air Molecules as Variations in Pressure.Practical Investigation: Pitch and Loudness of a Sound.Resonance in Mechanical Systems (Driving Frequency, Natural Frequency, Amplitude, Transfer of Energy).Reflection, Refraction, Diffraction and Wave Superposition.Graphs of Displacement as a Function of Time (Transverse and Longitudinal Waves).Practical Investigation: Transverse, Longitudinal, Mechanical and Electromagnetic Waves.Practical Investigation: Creation of Mechanical Waves.
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