In a thin film of oil on water, if the thickness of the film is 200 nm, what is

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Question: In a thin film of oil on water, if the thickness of the film is 200 nm, what is the condition for the first order bright fringe?

Options:

Correct Answer: 2t = mλ

Solution:

For constructive interference in a thin film, the condition is 2t = mλ, where m is an integer.

In a thin film of oil on water, if the thickness of the film is 200 nm, what is the condition for the first order bright fringe?

In a thin film of oil on water, if the thickness of the film is 200 nm, what is the condition for the first order bright fringe?

Step 1: Understand that we are dealing with a thin film of oil on water.
Step 2: Know that the thickness of the oil film is given as 200 nm.
Step 3: Recognize that we want to find the condition for the first order bright fringe.
Step 4: Remember the formula for constructive interference in a thin film: 2t = mλ.
Step 5: Identify that 't' is the thickness of the film (200 nm) and 'm' is an integer representing the order of the fringe.
Step 6: For the first order bright fringe, set m = 1.
Step 7: Substitute the values into the formula: 2(200 nm) = 1λ.
Step 8: Simplify the equation to find λ: λ = 400 nm.

Thin Film Interference – The phenomenon where light waves reflected from the top and bottom surfaces of a thin film interfere with each other, leading to constructive or destructive interference based on the film's thickness and the wavelength of light.
Constructive Interference Condition – The specific condition for bright fringes in thin films, given by the equation 2t = mλ, where t is the film thickness, m is the order of the fringe, and λ is the wavelength of light.