Why Is m Equal to 1 for Minimum Thickness in Thin Film Interference?

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In summary, to calculate the minimum thickness of a thin film of turpentine on a lanthanum flint glass plate in order for it to appear green when viewed from above in white light, the equation 2t(n)=mλ is used, where n is the refractive index of turpentine (1.36), λ is the wavelength of green light (560nm), and m is the number of times light travels through the film before reaching the observer's eye. In this case, m is equal to 1 because the thickness must be the minimum possible for the film to appear green, and thickness is directly proportional to m. Additionally, m can only be an integer.
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math10e
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wavelengths-->calculating "m"

A thin film of turpentine (n=1.36) covers a lanthanum flint glass plate (n=1.80). What is the minimum thickness the film should have if it is to appear green (wavelength=560nm) when viewed from above in white light? (answer=206nm)


Use the equation 2t(n)=mλ



I know that it would be 2t(1.36)=1(560), but why is "m" 1? I know that there is a 180 degree phase change making the waves constructive...but does m=1 only because there needs to be some light emitted?
 
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because you have to find minimum thickness, thickness is directly proportional to m and m can only be an integer :wink:
 

FAQ: Why Is m Equal to 1 for Minimum Thickness in Thin Film Interference?

What is the formula for calculating wavelength?

The formula for calculating wavelength is λ = c / ν, where λ is the wavelength in meters, c is the speed of light (3.00 x 10^8 m/s), and ν is the frequency in hertz (Hz).

How do I convert frequency to wavelength?

To convert frequency to wavelength, use the formula λ = c / ν, where λ is the wavelength in meters, c is the speed of light (3.00 x 10^8 m/s), and ν is the frequency in hertz (Hz). Simply plug in the given frequency and solve for λ.

What unit is used to measure wavelength?

The unit used to measure wavelength is meters (m). This is because wavelength is a measure of distance, specifically the distance between two consecutive peaks or troughs in a wave.

What is the relationship between wavelength and energy?

The relationship between wavelength and energy is inverse. This means that as wavelength decreases, energy increases and vice versa. This is known as the wavelength-energy relationship and is described by the formula E = hν, where E is energy in joules (J), h is Planck's constant (6.63 x 10^-34 J*s), and ν is frequency in hertz (Hz).

How do I calculate the wavelength of a specific color of light?

To calculate the wavelength of a specific color of light, you can use the formula λ = c / ν or you can refer to a wavelength-color chart that lists the approximate wavelengths of different colors of light. Keep in mind that the exact wavelength of a color may vary slightly depending on the source of light and other factors.

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