# Light Waves, Color, and Soap Bubbles

• beefcakes_mcg
In summary, a soap bubble with an index of refraction of n = 1.33 reflects red and violet light but not green light due to destructive interference between the waves reflected from the front and back surfaces of the bubble's wall. The minimum thickness of the bubble can be computed by considering the interference of the smallest possible wavelength that includes both red and blue cones, taking into account the slower speed of light in the soap material, and assuming the soap bubble must be one wavelength long.
beefcakes_mcg

## Homework Statement

A soap bubble is floating in the air. The wall of the bubble
has an index of refraction of n = 1.33. It is observed that red and
violet light are reflected from the surface of the bubble, but no
green light is reflected. Compute the minimum thickness of the
bubble.

v=fλ
c=3x10^8

## The Attempt at a Solution

I'm pretty much just confused on where to start. I'm assuming it has something to do with the color destructively interfering with the soap bubbles, so that only some of the color reflects. Do I start by picking the smallest possible wavelength that includes both red and blue cones, and then assume that the speed of light is slower due to the soap material, THEN assume that the soap bubble has to be one wavelength long?

beefcakes_mcg said:
I'm pretty much just confused on where to start. I'm assuming it has something to do with the color destructively interfering with the soap bubbles, so that only some of the color reflects. Do I start by picking the smallest possible wavelength that includes both red and blue cones, and then assume that the speed of light is slower due to the soap material, THEN assume that the soap bubble has to be one wavelength long?

There is interference between the waves reflected from the front surface and the back surface of the wall of the bubble. The interference is destructive for green light.

ehild

## 1. What are light waves?

Light waves are a form of electromagnetic radiation that travels in a straight line at a speed of approximately 186,000 miles per second. They are responsible for the sensation of sight and consist of different wavelengths that determine the colors we see.

## 2. How do light waves create color?

Light waves create color by reflecting off of objects and entering our eyes. The objects absorb some of the wavelengths of light and reflect others, which our eyes interpret as color. The colors we see depend on the wavelengths of light that are reflected.

## 3. What is the color spectrum?

The color spectrum is the range of colors that are visible to the human eye. It is made up of all the different wavelengths of light, with red having the longest wavelength and violet having the shortest. The colors in between are orange, yellow, green, blue, and indigo.

## 4. How do soap bubbles create colorful patterns?

Soap bubbles create colorful patterns because of the thin layer of water and soap molecules that make up the bubble. When light hits the bubble, it is reflected and refracted, creating interference patterns that produce multiple colors. The thickness of the bubble determines which colors are most visible.

## 5. Why do soap bubbles change color as they pop?

Soap bubbles change color as they pop because the thickness of the bubble decreases as it shrinks. This causes the interference patterns to change, resulting in a different color being reflected. As the bubble gets smaller, the colors become more vibrant until it eventually disappears.

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