How do we get radio programmes in our radio sets?
Energy comes in two basic forms: “Potential” and “Kinetic”
Potential Energy is any type of stored energy; it is not shown through movements. Potential Energy can be chemical, nuclear, gravitational or mechanical.
Kinetic Energy is the energy of movements: motion of electrons in electricity, vibrations of atoms by a sound wave etc.
Each form of energy can be transformed into any other form of energy. But energy is not destroyed or created. Sound is a mechanical form of energy (i.e. potential energy) which travels in the form of a wave which is made through the transmitted vibration of atoms in bulk. This mechanical wave is an oscillation of pressure. This pressure created by sound could be used to convert it into electrical energy according to law of thermodynamics.
Electric energy is the kinetic energy, of moving electrons, the negatively charged particles in atoms. Sound waves are not converted into radio waves. First, sound waves are converted into electrical signal using a microphone. Then this mild signal is amplified (intensified). Now a high frequency radio wave is modulated with this amplified signal. This modulated radio wave is then propagated through space. The receiving radio set converts these electromagnetic waves into electrical energy and further to sound waves.
Sound waves have different frequencies and wave lengths (related to pitch) and different magnitudes (related to how loud). Based on this, earlier Amplitude Modulation (AM) was used in Radio. But when Frequency Modulation was invented, which was useful in reducing static and interference from electrical equipment and atmosphere, is in use now a days. Later in 1960 a pocket size transistorized radio was also invented.
It is important to understand that our radios are only receivers. The radio stations that create various programmes have powerful transmitters and they also have receivers to talk to the public. But our mobile phones have receivers and transmitters.