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CHAPTER - 6

CHAPTER - 6. SPECTRUM . The sequence of violet , indigo , blue , green , yellow , orange and red colour is called spectrum. DISPERSION. The phenomenon of splitting of white light into its constituent colours is known as DISPERSION. DEVIATION.

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CHAPTER - 6

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  1. CHAPTER - 6 SPECTRUM

  2. The sequence of violet, indigo, blue, green, yellow, orange and redcolour is called spectrum

  3. DISPERSION • The phenomenon of splitting of white light into its constituent colours is known as DISPERSION

  4. DEVIATION The angle between the incident ray and the emergent ray is called the angle of deviation. It is represented by d

  5. DISPERSION DISPERSION OF WHITE LIGHT THROUGH A PRISM

  6. CAUSE OF DISPERSION When white light is incident on the first surface of a prism and enters it, light of different colours is refracted (or deviated) through different angles.

  7. RECOMBINATION OF COLOURS

  8. FACTORS AFFECTING ANGLE OF DEVIATION • The angle of incidence at the first surface (i) • The angle of Prism (A) • The R.I. of the material of the prism (μ)

  9. BROAD CLASSIFICATION OF ELECTROMAGNETIC SPECTRUM

  10. FREQUENCY AND WAVE LENGTH OF VISIBLE SPECTRUM C = λf C= speed of light. λ = wavelength of light f = frequency of light

  11. INVISIBLE SPECTRUM THE REGIONS OF THE SPECTRUM WHICH DO NOT EXCITE THE RETINA, AND HENCE, ARE NOT VISIBLE ARE COLLECTIVELY CALLED THEINVISIBLE SPECTRUM

  12. TYPES OF INVISIBLE SPECTRUM • RADIO WAVES. • MICROWAVES. • INFRARED RADIATION. • ULTRAVIOLET RADIATION. • X-RAYS. • GAMMA RAYS. (Increasing frequency and decreasing wavelength)

  13. RADIO WAVES • Have longest wavelength(above 10m). • Frequency below 30 MHz. • Produced by Oscillating circuits in special vacuum tube. • Used mainly in RADAR communication, RADIO and TELEVISION communication.

  14. MICROWAVES • Wavelength is between 1cm to 0.1mm. • Its frequency between 3x1010Hz to 3x1011Hz. • Produced by Oscillating circuits in special vacuum tube. • They are used for T.V. communication purpose for long distance telephony, telegraphy, etc. • They are also used for cooking, in microwave ovens.

  15. INFRARED RADIATION The electromagnetic radiations beyond red end of the visible spectrum are called infrared radiations and the spectrum is called Infrared spectrum.

  16. PROPERTIES • They are not affected by electric or magnetic field. • They travel with the velocity of light. • They obey the laws of reflection and refraction. • They are least scattered by fog, mist, etc.

  17. Their wavelength is between 0.8μm to 40μm. • They do not affect ordinary photographic film. • They can be detected by a thermopile or a thermometer.

  18. USES OF INFRARED RADIATION • Due to its heating effect, they are used by the doctors for therapeutic purpose. • They can be used for taking infrared photographs with suitable photographic plates and filters in foggy weather. • They are used to detect diseases in crops.

  19. ULTRAVIOLET SPECTRUM The region of spectrum which extends beyond the violet colour of the visible spectrum is called ultraviolet spectrum.

  20. PROPERTIES • They are e.m.waves and are not effected by electric or magnetic field. • They travels with the velocity light. • The range of these radiations is between 4000A to 100A • They produce chemical effect in sliver.

  21. PROPERTIES • They obeys the laws of reflection and refraction. • They are absorbed by the atmosphere and convert oxygen to ozone. • They produced fluorescence in substance like zinc sulphide, barium sulphide, etc.

  22. USES OF U.V. RADIATION • U.V. Radiations when absorbed by the skin, stimulate the body to produce vitamin D. • They are used for sterilizing surgical instruments and drinking water. • U.V. Radiation are used to detect adulteration in ghee.

  23. USES OF U.V. RADIATION • U.V. Radiations are used to detected forgery of cheques or important documents. • U.V. Radiations are used for detecting original diamonds from fake diamonds.

  24. SOURCES OF U.V. RADIATION • Any source of light at a temperature of more than 25000C is a good source of U.V. Radiation. • Electric spark or electric arc lamp produce large amount of U.V. Radiation.

  25. X- RAY They are produced by excitation of inner electrons of an atom and sudden annihilation of high energy free electron.

  26. PROPERTIES • X-Ray are e.m.wave of very short wavelength ranging from 10-12m to 10-10m. • They are not effected by electric and magnetic field. • They effect the photographic plate intensely.

  27. PROPERTIES • They travel in vacuum with the speed of light. • They ionize the gas through which they pass. • X-ray undergo reflection and refraction.

  28. APPLICATION • X-Ray are used in surgery for the detection of fractures. • Use for studying atomic arrangement in crystals as well as in complex molecules. • Used in engineering for detecting faults , cracks and gas pockets in finished metal products. • Also used by detective departments for detection of explosives.

  29. GAMMA RAYS Gamma rays were discovered by Rutherford. They are emitted from the nuclei of some radioactive elements and are e m wave of very short wave length.

  30. Properties • Have velocity equal to that of light. • Have high penetrating power. They can penetrate through several centimeters thick iron and lead blocks. • They have got small ionizing power. • They can effect a photographic plate.

  31. Properties • They can produce heating effect in the surface exposed to them. • They are not deflected by electric and magnetic fields. • They knock out electrons from the surface on which they fall.

  32. Applications • Used in radiotherapy. In hospitals gamma rays are used to treat cancer and tumors. • In food industry, soft gamma rays are used to kill microorganisms. • Gamma rays are used to produce nuclear reactions.

  33. SCATTERING OF LIGHT Scattering is the process of absorption and then re-emission of light energy

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