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what really happens when light hits on a opaque object ? when light hits on a opaque object where does the light go ? Does the law of coservation of energy true here ?

what really happens when light hits on a opaque object ? when light hits on a opaque object where does the light go ? Does the law of coservation of energy true here ?

Grade:12

2 Answers

Sumit Majumdar IIT Delhi
askIITians Faculty 137 Points
9 years ago
Dear student,
When light hits an opaque object, all the light is absorbed, except that portion of the spectrum of light which matches the object's color. That particular bandwidth is reflected. For example, a yellow object appears yellow, and a blue object appears blue. Black objects absorb light without reflecting any, while white objects reflect almost all the visible light which strikes them.
Regards
Sumit
Aziz Alam IIT Roorkee
askIITians Faculty 232 Points
9 years ago
Reflection and transmission of light waves occur because the frequencies of the light waves do not match the natural frequencies of vibration of the objects.When light waves of these frequencies strike an object, the electrons in the atoms of the object begin vibrating. But instead of vibrating in resonance at a large amplitude, the electrons vibrate for brief periods of time with small amplitudes of vibration; then the energy is reemitted as a light wave. If the object is transparent, then the vibrations of the electrons are passed on to neighboring atoms through the bulk of the material and reemitted on the opposite side of the object. Such frequencies of light waves are said to be transmitted
If the object is opaque, then the vibrations of the electrons are not passed from atom to atom through the bulk of the material. Rather the electrons of atoms on the material's surface vibrate for short periods of time and then reemit the energy as a reflected light wave. Such frequencies of light are said to be reflected.
Energy Conservation is valid.Energy of light incident is equal to energy of light transmitted, light absorbed and light reflected.
Each obeject in this world reflects,transmits & absorbs, whether an object is opaque or transparent depends upon how much light is reflected, transmitted and absorbed.

Thanks & Regards
Aziz Alam
IIT Roorkee
askIITians Faculty

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