Physics Formulas for Waves
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Angular frequency |
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f = frequency |
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Speed of any wave |
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Relation between wavelength and the propagation constant |
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Displacement function for a wave on a string |
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A = amplitude
moving right |
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Speed of a wave on a string |
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T = tension |
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Average power transmitted by a wave on a string |
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Displacement function for a standing wave |
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Allowed wavelengths for standing waves with displacement nodes at each end |
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n = 1, 2, 3, . . . L = length of string or pipe |
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Allowed wavelengths for standing waves with a displacement node at one end and an antinode at the other |
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m = 1, 2, 3, . . . |
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Description of a one-dimensional sound wave |
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Displacement |
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Speed of sound |
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γ = ratio of specific heats P = pressure ρ = density |
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Pressure amplitude of a sound wave |
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k = Boltzmann’s constant P0 = ambient pressure |
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Index of refraction |
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Where c is the velocity of light in a vacuum and v is the velocity of light in the medium |
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Intensity of a sound wave |
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Sound intensity level |
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dB is decibels I in W/m2 |
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Inverse square law for intensity |
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where r1 and r2 are two different radii from a point source |
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Doppler effect for sound |
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Doppler effect for light |
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vradial << c |
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Relativistic Doppler effect for light |
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for a blueshift Change the sign of vradial for a redshift |
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Law of reflection |
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Snell’s law |
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Superposition of Two Harmonic Wave Functions |
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Δφ = phase difference between the two harmonic wave functions |
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Maxima for 2 Slit Interference |
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d = separation between slits θ = angle from the center line m = 0, 1, 2, . . . |
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Minima for 2 Slit Interference |
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m = 0, 1, 2, . . . |
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Diffraction Minima for Rectangular Slit |
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a = slit width θ = angle from the center line m = 0, 1, 2, . . . |
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First Diffraction Minimum for a Circular Aperture |
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a = aperture diameter θ = angle from the center line |
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Image in a Plane Mirror |
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Image Formed by Plane Refracting Surfaces |
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Image Formed by a Spherical Mirror |
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f = focal length r = radius of the spherical mirror |
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Lens Maker’s Equation |
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n = index of refraction of the lens material
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Image Formed by a Thin Lens |
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Magnification of an Image |
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= observer velocity relative to air
= radius of the front surface
= radius of the back surface
= index of refraction of the outside medium
