- #1

catalyst55

- 24

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I know photons have what is termed as 'moving mass', but what exactly does this mean? And what implications does it have?

I recently did a question where i had to work out the force green light exerted on a mirror. I did this by finding the momentum of the photons, calculating their change in momentum as they hit the mirror, and the using Newton's second law (F=dp/dt) to find the force on the mirror -- and the answer was to the order of magnitude 10^-3 N! Hey! That's quite a lot, don't you think?

I find it incomprehensible that light exerts a force on a mirror of order of magnitude 10^-3. If it was of order of magnitude 10^-30 or 10^-20 (ie miniscule), then i'd be able to reconcile it with my intuition, but this i just can't.

Perhaps this is just something that cannot be considered intuitively?

Anyways, here's my hypothetical question:

If I was stationary in space (perfect vacuum, g=0 N/kg -- not that it matters) relative to, say, the Earth, and i shone a REALLY powerful (ie intense -- lots of photons emitted) torch, would i accelerate as a result of shining the torch?

Trying to get my head around it, hehe...

Cheers

I recently did a question where i had to work out the force green light exerted on a mirror. I did this by finding the momentum of the photons, calculating their change in momentum as they hit the mirror, and the using Newton's second law (F=dp/dt) to find the force on the mirror -- and the answer was to the order of magnitude 10^-3 N! Hey! That's quite a lot, don't you think?

I find it incomprehensible that light exerts a force on a mirror of order of magnitude 10^-3. If it was of order of magnitude 10^-30 or 10^-20 (ie miniscule), then i'd be able to reconcile it with my intuition, but this i just can't.

Perhaps this is just something that cannot be considered intuitively?

Anyways, here's my hypothetical question:

If I was stationary in space (perfect vacuum, g=0 N/kg -- not that it matters) relative to, say, the Earth, and i shone a REALLY powerful (ie intense -- lots of photons emitted) torch, would i accelerate as a result of shining the torch?

Trying to get my head around it, hehe...

Cheers

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