Light and Sound
Light and sound are important in our life. Light stimulates the sense of seeing while sound is sensed by the sense of hearing. Both of them are waves. Sound is made of mechanical wave while light is made of electromagnetic waves.
The waves of light travel transverse to the direction of propagation. The speed of light is free of wave frequency when it passes through an empty space. The speed of light in vacuum and air is about 3×(10)8 ms-1. The remarkable fact about light is that it is a wave and at the same time it has the properties of the particles. Light can be absorbed in the form of energy packets known as ‘photons’. It may be emitted. Light exhibits the properties such as frequency, direction, intensity and polarization.
Sound is caused by mechanical vibrations travelling through all forms of matter, gases, solids, liquids etc. it requires some kind of media to travel. It cannot be travelled in vacuum. Sound is made up of longitudinal waves. It means that there are alternate compressions and expansions of matter parallel to the direction of waves. Sound is transmitted in longitudinal as well as transverse waves in solid material or medium. It can travel in gas and liquids in longitudinal waves only. Some factors like the ratio of density and pressure of the medium and the temperature of the medium affect the speed of the sound.
Difference between Light and Sound
Light can travel in empty space. No medium is required for light to travel. But sound cannot travel without a medium which may be solid, gas or liquid. Light cannot travel through opaque while it is no barrier for sound. Both light and sound suffer a speed loss, absorption and change of direction. They both are affected by the frequency. A slight change in frequency of sound creates a sensation while a change in the frequency of light can change the sensation of our eye. For example, various colors of light have different frequencies. Both of them are waves. However, light has the nature of particles too. Speed of sound depends upon the properties of it medium while the speed of light is constant in air and empty space. Both are opposite to each other. The denser is the medium, the greater will be the speed of sound. It is exact opposite in case of the light.