Hallo to all members, this is my first post.(adsbygoogle = window.adsbygoogle || []).push({});

1. The problem statement, all variables and given/known data

A short Laser flush with the Energy E = 1J hits a ideally reflecting mirror, with mass [tex] m_m = 2 * 10^(-5) kg [/tex]. The light has a wave length of 696 nm. The mirror is hanging on a rope with the length l = 0,1m.

2. Relevant equations

How big is the deflection of the mirror.

3. The attempt at a solution

I think that tan [tex]\alpha \approx F_G/F_L[/tex], where F_G is the Gravitation, F_L the Force caused by the Photons. So I try to get F_L. According to the law of conservation of momentum:

[tex]I_s = 2 p_l;[/tex]

I_s is the impulse on the mirror and p_l is the sum of all photons' momentum. I take it twice, one time when they arrive at the mirror, a second time when they are reflected.

[tex]I_s = h/(\lambda) = F * dt[/tex] so

[tex]F = h/(\lambda * dt)[/tex].

I do not know how to get a time, to get the force acting on the mirror

Maybe my approach is completely false, please tell me then.

Thanks and Greetz,

caspar

p.s. excuse my English, I am not a native speaker

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# Homework Help: Flash of a laser moves a mirror hanging on a rope

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