Difference Between Light and Sound

Light vs Sound

Light and sound play a vital role in human life. Light triggers the sensation of seeing and sound stimulates the hearing. They are both waves. Light falls into the category of electromagnetic waves, while sound is a mechanical wave.

Light

光线是最familiar form of electromagnetic waves. Light travels as transverse waves; transverse to the direction of propagation. In empty space, where there is no substructure, the speed of light is independent of wave frequency. Light travels through air and vacuum at an speed of around 3 x (10)⁸ms^-1. Apart from being a wave, light exhibits properties of particles. Light can be emitted and absorbed as tiny energy packets named “photons”. Intensity, frequency or wavelength, direction and polarization are some of the primary properties of light.

Sound

Sound can be interpreted as mechanical vibrations that travels through all forms of matter : gases, liquids, solids and plasmas. Presence of atoms, molecules or some structure is necessary for sound to travel; it corresponds to the propagation of a disturbance through a medium. Sound is composed of longitudinal waves (also called compression waves), that is, alternate compressions and expansions of matter parallel to the direction of wave. Through gases, liquids and plasmas sound can be transmitted as longitudinal waves, while through solids, it can be transmitted as both longitudinal and transverse waves. It is the properties of sound waves that characterize sound namely frequency, wavelength, amplitude, speed and etc. Speed of sound depends on the ratio of density and pressure of the medium and also the temperature.

Difference between Light and Sound

Light and sound both are waves, but sound requires a material medium to travel, and hence cannot travel in empty space while light can travel through vacuum but not through opaque materials. Both undergo refraction, diffraction and interference. While propagating at the interface of two media, both light and sound suffer loss of speed, change in direction or get absorbed. Frequency or wavelength affects both of them. A change in frequency of sound waves creates an audible sensation ( a difference in pitch) and a change in the frequency of light wave causes a visual sensation (a difference in color). There are several dissimilarities between light and sound. Although both are waves, light exhibits particle nature too. Speed of light in air and empty space is a fundamental constant, whereas speed of sound depends heavily on the properties of the medium. The denser the medium, the greater is the speed of sound. The opposite is true for light. Sound consists of longitudinal waves whereas light consists of transverse waves which give light the ability to be polarized.

In brief: Light vs. Sound - 声音只是波浪，而光同时表现出波和粒子特性。 – Sound is a longitudinal wave, but light is a transverse wave. – Sound needs a material medium to travel, light can propagate through vacuum also. – Light travels much faster than the sound. Scientists have achieved the speed of sound, but still they are unable to go past the speed of light.