PROPERTIES OF WAVES AND LIGHT

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Properites of Waves
Properties of Waves

In this courses you will cover the topics related to the properties of waves, namely:

  • Wave motion: e.g. vibrations in ropes, Springs
  • Different types of wave: Transverse (water and light waves) and Longitudinal (sound waves) in terms of direction of oscillation
  • The wave equation: Displacement-time and displacement – distance graphs of a wave. (Use the equation v = fl.)
  • Use of waves in our life: radio, television, ultrasonic etc.
  • Scientific terms: Propagation-transmission, reflection- and refraction of waves. Diffraction of waves using wide, narrow gaps, sharp edges.
  • Two types of Interference of waves: such as Constructive and destructive
  • The characteristics of sound waves: Loudness of sound and its amplitude
  • Pitch of sound and its frequency
  • Factors which influence the quality of sound: such as overtones or wave form of the note
  • Production of sound using vibrating objects
  • Sound wave essentials: rarefactions (stretches) and compressions (“Squashes”)
  • Range of audible sound frequencies (20Hz to 20000Hz)
  • Effects of sound waves traveling through air and a vacuum
  • Speed of sound in air (approximately 330m/s)
  • Respective speeds of sound in solids, liquids and gases
  • The characteristics of sound waves: Loudness of sound and its amplitude
  • Pitch of sound and its frequency
  • Factors which influence the quality of sound: such as overtones or wave form of the note

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Course Content

SIMPLE IDEAS OF WAVE MOTION
Waves mean transmission of energy from one place to another. The amazing fact here is that the particles of the medium do not travel with the wave. In addition to transmission of energy, transmission of information too takes place in a wave. Naturally occurring waves as well as those produced by us are divided into two main groups, namely mechanical waves and electromagnetic waves. Mechanical waves are produced by the vibration of particles of matter in specific modes and this material medium is essential for its transmission. These media could be solid, liquid or gas. When the wave travels, if the particles of the medium vibrate perpendicularly to the direction of the motion of the wave, then the wave is termed a 'transverse wave', while if the vibration of these particles is along the direction of motion of the wave, the wave is termed a 'longitudinal wave'. You can observe the ripples on water when the surface of water in a pond is made to vibrate by dropping a stone on it or by other means. Observe well the rising and falling of water surface even at places away from the point where the disturbance is affected. Transverse waves A transverse wave is a wave where the movement of the particles of the medium is perpendicular to the direction of propagation of the wave. Concepts addressed include: wavelength, amplitude, frequency, period, crests, troughs, points in phase and points out of phase, the relationship between frequency and period, i.e. 1 Longitudinal waves In a longitudinal wave, the particles in the medium move parallel to the direction in which the wave moves. It is explained how to generate a longitudinal wave in a spring. While transverse waves have peaks and troughs, longitudinal waves have compressions and rarefactions. A compression and a rarefaction is defined, explained and illustrated. Similar to the case of transverse waves, the concepts wavelength, frequency, amplitude, period and wave speed are developed for longitudinal waves. Problems set on the equation of wave speed for longitudinal waves, V=f λ , concludes this section.

  • Concepts of Wave (Introduction)
    00:00
  • The behaviour of waves
    00:00

SOUND WAVES
Sound is a longitudinal wave which fulfils important requirements in our lives. It affords opportunity to communicate ideas and also to appreciate and enjoy music. Sound is always produced by the vibration of some object. This could be a membrane or a string. When the membrane or the string vibrates, layers of air around it too vibrate longitudinally to produce sound. Accordingly, it is apparent that a medium is essential for transmission of sound. It would be possible for you to find examples to show that sound travels faster in water and in solid media than in air. The human ear is sensitive to sound waves only within the frequency range of 20 Hz – 20000Hz, while it has been found that certain animals have sensitivity towards sound waves even outside this range. Sound waves of frequency higher than 20000 Hz are known as ultrasonic sound wave and are utilised in medical activities, oceanic investigations and fisheries. Sound is a longitudinal wave. The basic properties of sound are: pitch, loudness and tone. Illustrations are Used to explain the difference between a low and a high pitch and a soft and a loud sound. The speed of sound depends on the medium the sound is travelling in. Sound travels faster in solids than in liquids, and faster in liquids than in gases. The speed of sound in air, at sea level, at a temperature of 21 C and under normal atmospheric conditions, is 344m/s. Frequencies from 20 to 20 000 Hz is audible to the human ear. Any sound with a frequency below 20 Hz is known as an infrasound and any sound with a frequency above 20 000 Hz is known as an ultrasound.

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