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Electromagnetic Waves — Physics STD 12 Science — Question

Rajasthan BoardEnglish MediumSTD 12 SciencePhysicsElectromagnetic Waves5 Marks
Question
Write the name of different waves in electromagnetic spectrum and give brief introduction of their discovery, wavelength range, properties and applications.
✓

Answer

1. $\gamma$ - Rays:
Wavelength range $10^{-13}$ to $10^{-10}$ metre.
Discovery - by Becquerel. (1896) and Curie (1898)
Production - By natural and artificial disintegration of radioactive substances.
Properties -They produce invisible, penetration and fluorescene, phosphorescence, ionisation and diffraction.
Applications-These are used to get the information about the structure of atomic nuclei.
2. X-Rays:
Wavelength range $10^{-10}$ to $10^{-8}$ metre.
Discovery-By Rontgen (1895)
Production - By bombardment of cathode rays on metal targets.
Properties-They are less penetrating than $\gamma$ - rays but more pennetrating than visible rays. They affect photographic plates. In human body tissues are transparent to them but bones are relatively opaque.
Applications - These are used to get the information about atomic structure and crystal structure and also used in medical diagnosis.
3. Ultraviolet Rays :
Wavelength range $10^{-8}$ to $4\times10^{-7}$ metre.
Discovery - Ritter (1802), Schuman (1890) and Lyman (1906).
Production - By electric discharge and vacuum spark.
Properties -They are very active. They show maxi-mum chemical effect and minimum heating effect.
Applications- These are useful in the detection of invisible writing, forged documents and finger prints.
4. Visible Rays (Light rays) :
Wavelength range $4\times10^{-7}$ to $7.8\times10^{-7}$ metre.
Discovery - Newton
Production - Reflection, refraction, interference diffration, polarisation, photo-electric effect, photographic action, sense of sight.
Applications -To see object by the eyes.
5. Infrared rays :
Wavelength range $7.8\times10^{-7}$ to $10^{-3}$ metre.
Discovery - By Herschell (1840)
Production - By heating the substance to a very high temperature.
Properties - Having more invisible penetrating effect on thermopile, bolometer.
Applications - These are used in revealing the secret writings on the ancient walls green houses to keep the plants warm and for looking through haze, fog or mist.
6. Radio Waves :
(a) Hertzian Waves or Short Radio Waves: i.e., Micro waves
Wavelength Range $10^{-3}$ to 1 metre.
Discovery - By Hertz (1888)
Image
Production - By spark gap.
Properties -They show reflection, refraction and interference.
Applications -These are used in radar and television.
(b) Long Radio waves or Wireless waves :
Wavelength range -104 metre.
Discovery - By Marconi (1896)
Production-When a ratio walve is used as an oscillator these waves are produced.
Properties-These waves are used in radio and wireless telegraphy. They show reflection, refraction and diffraction.
Applications-These are used in radio broadcasting.

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