Dispersion of light

1. Dispersion of light

2. Monochromatic light • Monochromatic light is the light consisting of one colouror one wavelength.

3. White light • White light consists of seven different visible colours, each colour having its own wavelength and it also consists of two invisible radiations situated at the two extreme positions.

4. Dispersion of white light • Dispersion of white light is the separation of white light into its components (seven coloursand two radiations).

5. Different colours and Radiations of white light • R (red) • O (orange) • Y (yellow) • G (green) • B (blue) • I (indigo) • V (violet) Two radiations • u.v (ultra violet) • I.r (Infra Red)

6. Dispersion of white light

7. Spectrum of white light • The patch of different coloursobtained on a screen after dispersion of white light is called the spectrum of white light.

8. Pure spectrum of white light • Spectrum of white in which there is a distinct separation between the different colours. Impure spectrum • Spectrum in which the colours are overlapped.

9. Electromagneticwaves(e.g light wave) Electromagnetic waves: • Can also travel in vacuum • Are transverse waves [progressive waves] • Vibrations are perpendicular to the direction of propagation • All electromagnetic waves have the same velocity of propagation in vacuum • e.gVelecity of propagation in air or vacuum = 3×108m/s • V= f λ • Electromagnetic waves of small  and high frequency are more penetrating.

10. Electromagnetic spectrum • A table showing the wavelength and frequency of different electromagnetic waves.

11. The different electromagnetic waves are: • γ- rays & X-rays • u.v-(ultraviolet) • v-R-(visible region) • I-R –(Infra red) • Microwaves/Radar waves • Radio waves

12. Lowest frequency Highest frequency violet red Shortest wavelength Longest wavelength

13. Ultraviolet Radiation • Solar energy travels through ultraviolet Radiation. Ultraviolet radiation of small wavelength can cause caneer ultraviolet radiation of long  is important for photosynthesis and vitamin D. • A mercury lamp produces ultraviolet radiation ultraviolet . Ultraviolet radiation can be deleted by: • A photo cell and • Because it fluorescence on a sheet of glass

14. Visible light • Monochromatic light has a single colour, a single wavelength and a single frequency. • White light is made up of 7 colours

15. Infra red Radiation • Infrared Radiation allows heat energy to travel in vacuum. • At relatively low temperature, heated objects will emit infrared radiation • Infrared radiation can be detected by • A thermometer with blackened bulb • Thermocouple • Dark surfaces are good absorbers and emitters of infrared radiation. • Polished surfaces are good reflectors of radiations.

16. Applications of the following electromagnetic wave • Radiowavesradio and television communication • MicrowavesSatellite television and telephone • Infra-redhousehold electrical appliances, television controllers and intruder alarms • Light (visible)optical fibres in medical uses and telephone • ultravioletsun beds, fluorexent tubes and sterilixtion • X-rayshospital use and engineering application, to scan firactures, etc • Gamma-raysin medical treatment