- #1
caspar
- 5
- 0
Hallo to all members, this is my first post.
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.
How big is the deflection of the mirror.
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
Homework Statement
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.
Homework Equations
How big is the deflection of the mirror.
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