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CBSE Class 12-science Answered

What is light? Like on burning the paper, wood or candle or even the heating elements gives out the light and heat energy. So want to know how is light formed? Or is there is a light present or some kind of trapped in these substances or what?
Asked by m_tauqeer_ | 25 Jan, 2018, 01:01: PM
answered-by-expert Expert Answer
Light is the form of energy and part of visible region of electromagnetic spectrum (wavelength 400 to 600 nm) .
 
thermal radiations from a substance is electromagnetic radiation because this energy is radiated due to vibration and rotation of atoms and molcules. 
When the temperature of the radiation emitting object exceeds 2000K, the vibration and rotation frequency will be in the range 1012 to 1013 Hz. Hence at this temperature > 2000K, thermal radiation that is radiated out  of this substance is in the visible range of electromagnetic radiation, hence we see the light when substances like  paper, wood, candle etc. are burning. Heating elements also reaches the temperature >2000K when they are heated. Hence thermal radiation coming out of heated elements is in the visible range of electromagnetic spectrum.
 
light is not present or trapped in substances as light. Energy contained in the substance is coming out as light energy when the temperature becomes more than 2000K
Answered by Thiyagarajan K | 25 Jan, 2018, 02:15: PM

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CBSE 12-science - Physics
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