Help with Newton's Rings Homework Questions

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The discussion centers on a student's struggle with applying formulas related to Newton's Rings in a homework assignment. The student has identified the relevant equations but is having difficulty achieving reasonable answers for the thickness of a planoconvex lens, its radius of curvature, and focal length. They mention the dark spot at the center and attempt to use the formula for thickness but find their results unsatisfactory. Additionally, they express a desire for assistance while acknowledging the importance of showing effort in problem-solving. Clarification and guidance on the application of the formulas are requested to help resolve these issues.
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Hi. I have some homework questions here that I need a little help on. I know the fomulae to use just do not know how to apply it properly. Any help will be appreciated.

In a Newton's Ring experiment, a planoconvex glass (n=1.54) lens having a diameter 14.3 cm is placed on a flat plate. When 585 nm light is incident normally, 8 bright rings are observed with the last one right on the edge of the lens, at r.

1. What is the thickness of the lens?
2. What is the radius of curvature of the convex surface of the lens?
3. What is the focal length of the lens?
 
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not that i can answer this but if you read the FAQ you are supposed to show some working or some effort to have started your problem, maybe if you do that you will have more of a chance of it being answered
 
Well I know that at the center there is a dark spot so to find the thickness of the lens I'd assume that t=m(lambda)/2n but I get an unreasonable answer. To find the radius of curvature I tried using r=sqroot(m(lambda)R/n therefore R=r^2/(m*lambda*n) but again I don't think I'm getting the right answer. I'm not trying to catch a break here. So any help will be appreciated.
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
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