Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: hamza on 19/09/2007 20:53:49
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What does the word intensity mean for a way, be it a light wave or a sound wave.. Does it mean the energy or what??
And for a sound wave what does the word pitch mean?? I mean will a sound wave of hight pitch sound louder ?
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Intensity of a sound basically means the variations of the air pressure that it produces as it passes.
This is quoted on a logarithmic scale as decibels one Bel being an increase of 10 times, starting from 0 db(20 µPa or in pre SI units .00002 dynes/cm^2) roughly the least sound that ours ears can detect to 194 db which is the maximum that can be sustained at normal atmospheric pressure.
The pitch is the frequency of the pressure variation scientifically measured in Hertz but referred to by musicians as tones semitones etc.
The range of frequencies that young ears can perceive ranges from about 40 Hz to 20 KHz but as you get older drops to about 4 KHz
to clarify one point the intensity in decibels refers to the power in the sound wave and is thus 20*log p1/p0 thus the maximum pressure is .00002 * 10^9.7 = 100000 Pa = 1 Bar
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In light, intensity is the power per unit area imparted to a surface by the light. The energy given to the surface by the light would be intensity added up for a length of time in which it was measured, multiplied by the area of the surface.
(There are actually other definitions of intensity when dealing with light, but the above definition is probably the most general).