In general does wave velocity remain constant or keeps changing
In general, the velocity of a wave remains constant for a given medium under specific conditions. This velocity is often referred to as the "wave speed" and is determined by the properties of the medium through which the wave is propagating.
For example:
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Mechanical Waves (such as sound waves): In a uniform medium, the speed of sound (the wave speed) remains relatively constant as long as the temperature, pressure, and composition of the medium remain constant. In air, for instance, the speed of sound is approximately 343 meters per second at room temperature. Changes in these factors can affect the wave speed, which is why sound travels faster in warm air than in cold air.
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Electromagnetic Waves (such as light): Electromagnetic waves, including visible light, travel at a constant speed in a vacuum, which is approximately 299,792,458 meters per second, denoted as 'c.' In other materials, like glass or water, the speed of light is slightly slower than 'c.' The wave speed for light in a particular material is determined by the material's refractive index.
However, there are situations in which wave speed can change:
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Dispersion: In some materials, the speed of waves may vary with their frequency. This phenomenon is called dispersion. For example, in a dispersive prism, white light is separated into its constituent colors because each color (corresponding to a different frequency) travels at a slightly different speed in the prism.
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Wave Interactions: When waves interact with each other, their combined effects can lead to changes in wave speed. For instance, when sound waves pass through air of varying temperatures, the refractive index changes, causing the sound waves to refract and leading to changes in their direction and speed.
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Doppler Effect: The Doppler Effect causes a change in wave frequency (and sometimes speed) when the source of the wave and the observer are in relative motion. This effect is commonly observed in sound and light waves.
So, while the wave speed is generally constant under specific conditions, various factors can lead to changes in the wave speed, making the behavior of waves a fascinating and diverse area of study in physics.