In a thin film of soap, which color appears at the center of the pattern due to

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Question: In a thin film of soap, which color appears at the center of the pattern due to destructive interference? (2023)

Options:

Correct Answer: Red

Exam Year: 2023

Solution:

At the center, destructive interference occurs for red light due to its longer wavelength.

In a thin film of soap, which color appears at the center of the pattern due to destructive interference? (2023)

In a thin film of soap, which color appears at the center of the pattern due to destructive interference? (2023)

Step 1: Understand that a thin film of soap can create colorful patterns due to light interference.
Step 2: Know that light waves can interfere with each other in two ways: constructive interference (where they add up) and destructive interference (where they cancel each other out).
Step 3: Recognize that different colors of light have different wavelengths, with red light having a longer wavelength compared to other colors.
Step 4: At the center of the soap film, the conditions are such that red light undergoes destructive interference, meaning it cancels out.
Step 5: Conclude that because red light is canceled out at the center, it is the color that does not appear there.

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 depending on the film's thickness and the wavelength of light.
Destructive Interference – Occurs when two light waves combine in such a way that they cancel each other out, typically when the path difference between the waves is an odd multiple of half the wavelength.
Wavelength and Color – Different colors of light correspond to different wavelengths, with red light having a longer wavelength compared to other visible colors.