How Is the Value of 'm' Determined in Interference Equations?

[hyde2042]

Homework Statement

http://i.imgur.com/xrba7.png

Homework Equations

I'm using this equation to find the thickness of the polymer.

[(m+(1/2)) λ = 2nt] (where "n" is the index of refraction and "t" is the thickness )

The Attempt at a Solution

I just want to know how m is determined. I've learned everything else, but I missed the first day on which m value to use and it's always just slipped my mind whenever I'm in class or lab.

Thank you for your time.

 

[ehild]

m is any integer, including zero. ehild

 

[hyde2042]

Thanks, but I'm still unsure as to why "0" is used in the solution instead of "1" or "2".

 

[ehild]

Thanks, but I'm still unsure as to why "0" is used in the solution instead of "1" or "2".

First: it is easier to make a thinner coating then a thick one.

Second: The reflectance depends on the wavelength, this function is about the form R=A+Bcos(4piND/lambda) (N is the refractive index, D the thickness). If the reflectance is zero at a specific wavelength, it stays low in the broadest wavelength range when D has the smallest possible value.
The figure shows the reflectance spectrum of two coatings, one 100 nm, the other 300 nm thick. Both have zero reflectance at 600 nm.


ehild

 

[asteriatic]

To determine the value of m in the given equation, you need to look at the specific experimental setup and conditions. The value of m represents the number of interference fringes that can be observed in the experiment. This value can vary depending on the type of light source, the properties of the material being studied, and the geometry of the setup. In some cases, m may be a whole number, while in others it may be a fraction or decimal.

To determine the exact value of m, you can use a variety of techniques such as measuring the distance between fringes, using a monochromatic light source, or adjusting the angle of incidence. It is important to carefully follow the instructions and procedures provided by your instructor or lab manual to accurately determine the value of m. Additionally, it is important to note that the value of m may vary for different experiments and materials, so it is important to determine it for each specific case.