Speeds of Waves

There are many different type of wave travelling through many different media. The speed of a wave depends on what type of wave it is and on the media through which it is travelling, in ways that sometimes seem contradictory. For instance, sound waves travel faster in glass than air, but light travels faster in air than glass. This is because of the different nature of each type of wave, with each type of wave being affected in different ways as it passes through each material.

In general the speed of mechanical waves – sound, transverse or compressional – is proportional to the square root of some elastic property of the medium, which measures the 'stiffness' of the bonds or interactions between neighbiouring atoms or molecules in the medium and inversely proportional to the amount of matter in the material, since mass measures the resistance of a material to movement or vibration. In general

Equations and speeds for various types of waves are shown in the table.

Type of Wave

Speed of Wave

Medium

Speed(m/s)

Sound

Air

340

Sound

Water

1500

Compression Waves in Solids

Clay

Sandstone

Limestone

Granite

Salt

1000

2000

4000

5000

6000

Shear or Transverse Waves in Solids

Clay

Sandstone

Limestone

Granite

Salt

600

1200

2400

3000

3600

Compression Wave

Bone

3000

Transverse Wave on String

Violin A – String

Violin G - String

288

128

Electromagnetic Waves

In material of refractive indexrelative to a vacuum

In the above table,= density,=Bulk Modulus,=Shear Modulus,=Young's Modulus,=tension,=elextric permittivity of space,=magnetic permeability of space.

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