Light

• Light is a form of energy which propagates as a non-mechanical waves (EM waves – Electromagnetic waves). This type of energy is called radiation. All sources of light produce radiant energy.  Wavelength of light lies between 3900 A°. (angstrom– unit of lenth) and 7800A°.
• Light requires no medium to propagate it can propagate in vaccum as well as in medium.
• The wavelength of visible light is very small about 4×10-7 m to 8×10-7m.
• Frequency of visible light varies from about 3800×10¹¹ Hz to about 7800×10¹¹ Hz. The corresponding wavelengths are 380nm to 780nm (nm- nanometre).
• The color sensation of eye is just dur to the different wavelengths of the light. It is divided into VBGYOR
  • V-  Violet- 380-450nm
  • B- Blue-   450-500nm
  • G- Green- 500-570nm
  • Y- Yellow- 570-590nm
  • O- Orange- 590-620nm
  • R- Red-    620-780nm
• Red color has maximum wavelength and lowest frequency and Violet has minimum wavelength and highest frequency. As we know that
  • f= c/ λ  ;      where f= frequency, c= speed of light = 3×10^8 m/s , λ = wavelength    Red color has the maximum wavelength so we use this color in traffic signals, ambulance so that the people who are very far from the signal could be able to see the signal.
• Dual nature of Light-  According to “Louis- Victor de Broglie” , Light behaves as waves as well as particles. In 1929 de Broglie was awarded the Nobel Prize for Physics for the discovery of wave nature of electrons