INTERFERENCE IN THIN FILMS
Objective: § What is the thin film? Interference in thin films What is a soap bubble? Why are soap bubbles colored? Changing color
What is the thin film? Soap bubbles and thin layers of oil floating on water surface are common examples of thin films. When light is reflected from such a thin film, we observe different colors.
INTERFERENCE IN THIN FILMS In thin films of soap and oil , visible color bands are the result of interference of light in thin films.
What is a soap bubble? A soap bubble is a very thin sheet of water sandwiched between two layers of soap molecules. The film of soapy water surrounds a bubble of air. Color, one of the most beautiful Aspects of bubbles, also provides us with an extremely accurate tool for measuring the thickness of the soap film.
Soap molecules have one end that repels water, and one that attracts it, and these molecules move to the inner and outer surfaces, thrusting their water-repelling ends out into the air, and their "heads" inwards.
Why are soap bubbles colored? The thickness of the film - or rather, its thinness - determines whether iridescence is apparent. Light is reflected from both the inner and outer surface of the soap bubble.
David Stein holds the Guinness World Record for the longest bubble, over 15 m long.
Changing color The colors of a bubble are dependent on the thickness of the film. A bubble becomes thinner and thinner as it dries out (due to evaporation), before finally popping. Cluster of soap bubbles. A variety of beautiful colors appear in the swirls. Often, just before bursting, the swirls will appear black.
where can we find the interference of light?
The recipe of soap, that I use in my project 1/2 (500 ml) cup dishwashing detergent 4 -1/2 (4. 5 liter) cup water 4 tablespoons (60 ml) glycerin (available in pharmacies or chemical supply houses) Measure out the water, detergent, and glycerin into container with a cover and stir gently. Note: The longer you let the mixture set, the larger the bubbles are and the longer they seem to last.
References http: //www. webexhibits. org/causesofcolor/15 E. html http: //www. exploratorium. edu/ronh/bubbles/ bubble_colors. html http: //www. citycollegiate. com/interference_t hin_films. htm http: //bubbleblowers. com/homemade. html
