Constructive wave interference problem

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The discussion revolves around calculating the wavelengths of light that undergo constructive and destructive interference when reflected from a glass sheet coated with a 505nm thick layer of oil with a refractive index of 1.42. For constructive interference, the calculated wavelengths are 717 nm and 478 nm, while for destructive interference, the wavelengths are 574 nm and 410 nm. However, the initial calculations were deemed incorrect, prompting a reevaluation of the refractive indices involved. The importance of the refractive index of oil compared to glass is highlighted, suggesting that it influences the interference outcomes. The conversation emphasizes the need for careful consideration of these indices in solving the problem accurately.
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Homework Statement



A sheet of glass is coated with a 505nm thick layer of oil (n = 1.42).

For what visible wavelengths of light do the reflected waves interfere constructively/destructively?

Homework Equations



For constructive interference

lamba=2nd/m

For destructive interference

lamba=2nd/(m-1/2)

The Attempt at a Solution



for constructive

2*1.42*505/(3 or 4) (since m=3 and 4 will give me a visible wavelength) lamba = 717 nm, 478 nm

for destructive

2*1.142*505/(3 or 4 + 1/2) (since m=3 and 4 will also give me a visible wavelength) lamba = 574, 410 nm

HOWEVER, they are wrong... so I am completely clueless of what to do next.. help please >.<
 
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throllen said:
A sheet of glass is coated with a 505nm thick layer of oil (n = 1.42).
Hint: How does the index of refraction of the oil compare to that of the glass. Does it matter?
 


glass is supposed to have a higher index of refraction.. yes it matters...
 


Hmmm... in that case your solution looks fine to me.
 
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