Solving for Visible Light Reflection/Transmission: A Homework Help Guide

In summary, when white light is shone on a oil film it reflects off in different colors depending on the wavelength of the light.
  • #1
Feodalherren
605
6

Homework Statement


An oil film (n = 1.45) floating on water is illuminated
by white light at normal incidence. The film is 280 nm
thick. Find (a) the color of the light in the visible spectrum
most strongly reflected and (b) the color of the
light in the spectrum most strongly transmitted. Explain
your reasoning.

Homework Equations



2t=m(λ/n)

Where t is thickness and m is the order number.

The Attempt at a Solution



I don't understand part b. I must have dozed off in class (it's an 8am class, don't judge!). How exactly would I go about determining this?
 
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  • #2
Does that mean you can do part (a)?
Part (b) uses the same principle ... how do you get resonant reflection off a thin film?
What happens when you don't have resonant reflection?
 
  • #3
Yes I could do part a).

What I'm confused about is the physics behind it. The first question was pretty straight forward plug and chug - I just needed to look for constructive interference patterns.

I guess you get it if you get constructive interference? But that would be the same question... Hmm I have no idea what happens. I must have completely missed this in class or the professor forgot to mention.
 
  • #4
Feodalherren said:
The first question was pretty straight forward plug and chug - I just needed to look for constructive interference patterns.

I guess you get it if you get constructive interference? But that would be the same question... Hmm I have no idea what happens. I must have completely missed this in class or the professor forgot to mention.
... OK. Potted lecture:

You light coming back at you from the top surface consists of waves that have been reflected off the top surface added to waves that have been reflected off the bottom surface of the film.

The wavelength where these waves constructively interfere is the dominant color reflected.

The wavelength where these waves destructively interfere is the dominant color transmitted.

http://farside.ph.utexas.edu/teaching/302l/lectures/node152.html
 
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  • #5
You're a God among men Simon! Thanks a bunch! Those links were really helpful and ringed lots of bells for me.

I still don't understand how destructive interference could possibly be related to the dominant color. That makes no intuitive sense to me at all. I thought destructive interference meant that the light got wiped out and we wouldn't see it.

I guess what I'm really saying is I don't understand the difference between the two questions.
 

What is visible light reflection and transmission?

Visible light reflection and transmission refers to the way light interacts with different materials. Reflection occurs when light bounces off a surface, while transmission occurs when light passes through a material.

Why is it important to understand visible light reflection and transmission?

Understanding these concepts can help us design and improve products such as mirrors, lenses, and eyeglasses. It also helps us understand how light behaves in our environment and how we perceive color.

What are the factors that affect visible light reflection and transmission?

The factors that affect visible light reflection and transmission include the angle of incidence, surface roughness, and the properties of the material such as its refractive index and absorption coefficient.

How can I calculate the amount of light reflected or transmitted?

You can use the equations for reflection and transmission coefficients, which take into account the angle of incidence and the properties of the material. These coefficients represent the percentage of light that is reflected or transmitted at a given interface.

Can visible light reflection and transmission be controlled?

Yes, they can be controlled by using different materials and surface treatments. For example, anti-reflective coatings can reduce reflection and increase transmission, while mirrors are designed to have a high reflection coefficient. We can also manipulate the angle of incidence to control the amount of light reflected or transmitted.

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