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# Does light experience friction?

Does light experience friction?

Asked rashmi (VIII B, KV AFS Bidar)

FRICTION  is defined as the force which opposes relative motion between two surfaces in contact.

If you mean friction in the normal sense as above (as discussed in class), then the answer is “NO“.

Light is a form of energy and not a particle. But it is true that light shows some particle behaviour also.

But, there is a slowing down when light interacts with matter. But, in a homogeneous medium, light has a constant speed. The speed of light is different in different medium.  If we go to the atomic or molecular picture of matter, then we can imagine that light is interacting with a molecule, during the time of interaction, the light can be assumed to have been absorbed by the particle and then it is re-radiated. the re-radiated light travels to the next atom and interacts/absorbed. this slows down the average speed of light, but is constant for a particular homogeneous medium.

The speed of light is maximum in vacuum where there is no matter for light to interact.

So, in between two atoms also, light travels with its branded 3L kmps speed.

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