Soap Film Interference

The interference colors from a soap film can be related to the thickness of the film by using the interference condition and noting that there is a 180 degree phase change upon reflection from the film surface, but no phase change for the reflection from the back surface. The color seen depends also upon the angle of view.

If the angle of incidence on the film is α = °, 如果入射角为α = °， 中文译文中的待填/计算数值依次对应：1：alp。实际数值以上方原输入框为准。

the index of refraction of the film is n = , 薄膜的折射率是 n = , 中文译文中的待填/计算数值依次对应：1：n。实际数值以上方原输入框为准。

the thickness of the film is d = micrometers 薄膜的厚度是 d = 微米 中文译文中的待填/计算数值依次对应：1：d。实际数值以上方原输入框为准。

and the order (#of wavelengths) m = 以及波长的顺序（即波长数）m = 中文译文中的待填/计算数值依次对应：1：m。实际数值以上方原输入框为准。

then the angle in the film is β = ° (from Snell's law) 然后，薄膜中的角度为 β = °（根据斯涅尔定律） 中文译文中的待填/计算数值依次对应：1：beta。实际数值以上方原输入框为准。

The wavelength for maximum reflection is 波长最大反射时的波长		= nm = 纳米 中文译文中的待填/计算数值依次对应：1：wr。实际数值以上方原输入框为准。

and the wavelength for maximum transmission is 并为最大传输波长是		= nm = 纳米 中文译文中的待填/计算数值依次对应：1：wt。实际数值以上方原输入框为准。

This is an exploratory calculation which will calculate the wavelengths for maximum reflection and transmission, the thickness of the film, or the angle of incidence. Enter the needed data and then click on the rectangle for the desired quantity in the active graphic above.

Notes: The range of parameters which gives reflected or transmitted light in the visible range (roughly 400 to 700 nm) is very limited. If no parameters are entered, their values will default to incidence at 30°, n=1.42, and reflection in the green at 550 nm. All parameters may be changed, but calculated wavelengths outside the visible may not be at all reliable since the values usually given for indices of refraction are for the visible range only. If you see a visible color reflected from a soap film, you can get an approximate wavelength from a diagram of spectral colors, but there is no simple way to determine what order of reflection you are seeing.

Large soap bubbles can be produced from a solution of dishwashing detergent and glycerine. Experimenting with mixtures can produce solutions that will make long-lasting bubbles. In these examples it is not evident what order of interference is being seen, but the colors range through the entire visible spectrum. 可以用洗洁精和甘油的混合液制作出较大的肥皂泡。实验不同混合比例可以得到能形成持久肥皂泡的溶液。在这些例子中，无法明显看出是哪种干涉顺序在发生，但所呈现的颜色覆盖了整个可见光谱。

Other soap film fringe images. 其他肥皂膜干涉图像

Reflection and interference from a soap film 从肥皂膜反射和干涉 These fringes were recorded with a camcorder. The soap film was formed by dipping a loop formed by thumb and forefinger into a concentrated solution of dishwashing detergent. Note that you see red at three different angles, showing that three orders of reflection have been spanned. Bands of color can also be seen if the film thickness is varying. Image courtesy of Brian Dalton. 这些条纹是用摄像机记录的。肥皂膜是通过将拇指和食指形成的环浸入浓缩的洗洁精溶液中形成的。请注意，你可以看到在三个不同的角度下出现红色，这表明已经覆盖了三个反射级。如果膜的厚度发生变化，也可以看到颜色条带。图片由Brian Dalton提供。