Calculating Thin Film Thickness Using Interference Patterns

AI Thread Summary
The discussion revolves around calculating the thickness of a thin film using interference patterns in a Michelson interferometer. Given a film with a refractive index of 1.60 and a shift of 8 bright fringes with light of wavelength 580 nm, the calculated thickness is 1.5 µm. The user seeks confirmation on the application of the formula for bright fringes and clarification on the conditions for using the formula for minima. The physics involved includes the principles of interference and how bright fringes are formed. Overall, the focus is on ensuring the correct application of formulas in thin film interference problems.
Jimbob999
Messages
26
Reaction score
2

Homework Statement


A thin film with an index of refraction of 1.60 is placed in one of the beams of a Michelson interferometer. If this causes a shift of 8 bright fringes in the pattern produced by light of wavelength 580 nm, what is the thickness of the film?1.5 µm
2.9 µm
3.9 µm
7.7 µm
16 µm

Homework Equations



2L = (m + 1/2) lambda/n2 (maxima - bright film in air)

The Attempt at a Solution


[/B]
2L = 8.5 (5.7x10^-7 / 1.6)

L = 1.5µm

I am just trying to find out whether I used the right formula here, as it states in the question 'bright fringes', so I am assuming that bright film in air formula applies.
Also how would I know to use the other formula for minima?

Thanks.
 
Physics news on Phys.org
What physics process is at work in this problem?
How do bright fringes come about?
 
Last edited:
andrevdh said:
What physics process is at work in this problem?
How do bright fringes come about?
Intereference, Interference?

But that doesn't really get me anywhere...
 
Anyone can help?
 
TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
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}...
Back
Top