Electromagnetic waves | Part 2 | Electromagnetic Spectrum, Gamma rays, X- rays

To view Electromagnetic waves Part 1 click the link below
Electromagnetic waves | Part 1

    Electromagnetic Spectrum

    Is defined as 'The orderly distribution (i.e., sequential arrangement) of electromagnetic waves according to their wavelengths (or frequencies) in the form of distinct groups having different properties is called as the electromagnetic spectrum.

    Note - 1. The main parts of the spectrum are: gamma radiation, X-rays, ultraviolet radiation, visible light, infrared radiation, microwaves, radio waves.

                2.The spectrum of electromagnetic radiation has no upper or lower limits i.e., sharp boundaries. All regions overlap.

                 3.The know electromagnetic waves have wavelength ranging from 6 ✕ 10^-13m to more than 10^4 m.

          S.I. unit : Hertz (Hz)

Diagram of Electromagnetic Spectrum

Types of Rays

Explanation their properties and their uses

          1) Gamma Rays (ɣ)

Explanation 

      1. Gamma rays are electromagnetic waves having wavelength ranging nearly from 10^-15m to 10^-10m.

      2. The gamma rays are high energy electromagnetic waves having very high frequency ranging nearly from 3 ✕ 10^18 Hz to 5 ✕ 10^20 Hz.

      3. Gamma rays are detected with Geiger Counter, photographic plate, fluorescence.

      4. These gamma rays are emitted from the nuclei of some radioactive elements such as uranium, radium etc.

      5. Gamma rays were discovered by Paul Ulrich Villard. 

 Properties

      1. Gamma rays have high penetrating power. They can penetrate through several centimeters of thick iron and lead blocks.

      2. They have moderate ionizing power.

      3. They can produce fluorescence in some substances like willemite, zinc sulphate, barium platinocyanide, etc.

      4. They can affect a photographic plate.

      5. Gamma rays are not detected by electric and magnetic fields.

      6. They knock out electrons from the surface on which they are incident.

      7. They produce heating effect on the surface exposed to them. 

      8. They cause photoelectric effect, Comption scattering and pair production.

Applications:

      1. Gamma rays are used in radiotherapy for the treatment of cancer and tumor.

      2. In food industry, gamma rays are used to kill micro-organisms.

      3. It helps to preserve the food stuff.

      4. Gamma rays are used to produce nuclear reaction. 

      5. Also used in gamma ray astronomy.

                   2) X- rays

Explanation 

      1. X- rays are electromagnetic waves having very short wavelength ranging nearly from 10^-11 m to 10^-8 m.

      2. The frequency range of X- rays is from 1 ✕ 10^16 Hz to 3 ✕ 10^19 Hz.

      3. They are produced, when fast-moving electrons are suddenly stopped by an obstacle.

      4. X- rays are produced in laboratory by Coolidge X-ray tube.

      5. X- rays are detected by ionization chamber, photographic plate, scintillation counters, semiconductor detector, etc.

      6. X- rays were discovered by Wilhelm Konrad  Rontgen in 1895.

Properties 

      1. X- rays can travel in vaccum with the speed of light.

      2. They are not deviated by electric and magnetic fields.

      3. They affect photographic plates.

      4. They ionize the gas through which they pass. 

      5. They produce fluorescence in many substances like zinc sulphate, barium platinocyanide etc.

      6. They travel in straight line, they cast the shadows of the objects falling in their path.

      7. X- rays can undergo reflection, refraction, interference, diffraction, and polarization.

      8. X- rays can penetrate through materials like paper, thin sheet of metal, wood, flesh, skin, etc. But they cannot penetrate denser objects, such as bones, heavy metals, etc.

      9. Prolong exposure can have injurious effect on human bodies.

     10. They cause photoelectric effect.

Note:- When electromagnetic radiation of very short wavelength is incident on metal surface, electrons are emitted from these surfaces. This phenomenon is called photoelectric effect.

 Uses

      1. In surgery, X-ray photographs are useful to detect bone fracture or the presence of foreign objects likes bullets or hidden metal in a human body. 

      2. They are used for detecting faults,  cracks, flaws and gaps in metals.  

      3. They are used to distinguish real diamonds, gems, from artificial ones.

      4. X- rays are used to detect the structure of crystals.

      5. X- rays are used to cure skin diseases and to destroy tumors in the body of the patient. 

      6. They are used for detection of explosives opium etc.

To see Electromagnetic Waves | Part 3 | Ultraviolet rays, Visible light, Infrared rays, Microwaves click the link below
Electromagnetic Waves | Part 3 | Ultraviolet rays, Visible light, Infrared rays, Microwaves