With new discoveries and innovations constantly being made, the study of Physics Topics remains a vibrant and exciting field of research.
What is the Range of Wavelength of X-ray? What are the Uses of Radio Waves?
Different types of electromagnetic waves, their wavelengths, sources and uses are given in the following table.
Electromagnetic waves | Wavelengths | Source | Uses |
Radio waves | 104 to 0.1 m | Accelerated charged particles moving through a conductor, electronic devices like LC oscillators | Radio waves are used in mobile phones, aviation, communication related to radio and television. |
Microwaves | 0.3 to 10-4 m | Different electronic gadgets. | Microwaves are used in radar, microwave ovens (wavelength = 0.122 m) for cooking, to investigate the atomic and molecular properties of matter. |
Infrared waves | 10-3 m to 7 × 10-7 m | Molecules of matter at room temperature, are the sources of such waves. | Infrared waves are used in infrared photography, medical treatment and vibrational spectroscopy. |
Visible light | 7 × 10-7 m to 4 × 10-7 m | Visible light is emitted due to transitions of electrons in atoms and molecules. | Radiations from this range of em spectrum is detect able by human eye. Human eye is most sensitive for green, yellow colours (wavelength = 5.5 × 10-7 m). Hence the colour of tennis ball is green or yellow. |
Ultraviolet rays |
4 × 10-7 m to 6 × 10-8 m
|
Sun is the main source of these radiations. | Ultraviolet rays stimulate the production of vitamin D in our skin and cure skin diseases (psoriasis, vitiligo). |
X-rays | 10-8 m to 10-11 m | When a stream of electrons with high kinetic energy is incident on a metal target, X-rays are emitted. | X-rays can identify bone structure and hence it is used for medical imaging. It is also used in radiation therapy to cure cancer, Gamma rays X-ray crystallography, etc. Living cells may be damaged if X-ray falls on them. |
Gamma rays | 10-11 m to 10-14 m | These radiations are emitted from radioactive substances. It is one of the constituents of cosmic rays. | Gamma rays are used in scientific investigations. Living cells suffer severe damages when exposed to gamma radiation. Penetration power of gamma ray is so high that only a thick layer of lead can block it. |
Today we know about the existence of the electromagnetic spectrum [Fig.]. In fact, the whole world is immersed in electromagnetic waves of different wavelengths. Sun is the main source of most of these waves. In the increasing order of frequencies, i.e., decreasing order of wavelengths, a few important em waves are: radio wave or Hertzian rays, microwave, infrared, visible light, ultraviolet rays, X-rays, gamma rays, cosmic rays, etc. which has been discussed in the previous table. There is no distinct line of demarcation of different electromagnetic waves which, almost invariably, overlap to some extent.
All electromagnetic waves are generated due to motion of accel-erated charges.
German physicist Heinrich Hertz, in 1888, first generated elec-tromagnetic waves in the range of radio waves on an experimental basis, and also made arrangements for identification of the wave. He took help of an oscillating electric dipole. Oscillating electric dipole of this type, is known as Hertzian oscillator or Hertzian dipole.
1. Most of the substances absorb infrared wave very easily. On absorbing infrared radiation, the internal energy of matter increases; hence there is rise in temperature.
2. Ozone layer in the upper atmosphere, mainly in strato-sphere, absorbs the ultraviolet rays and converts to infrared rays. Some chemicals reduces the density of the ozone layer by reacting with it. These substances are called ozone depleting substance or ODS in short. Most of the ODS are made artificially and used in aerosol spray can and refrigerant. Uses of this type of matter is trying to be banned.