Due to interference, a thin film reflects no orange light...it appears dark. If you double its thickness and illuminate it again with orange light, what will you see? Choose one answer only.
It will appear dark again.
It will appear bright (strongly reflecting the orange light).
It could be either bright or dark, depending on the film.
How can I solve this?
A steel tube, which is closed at both ends, is filled with air. The air in the tube is vibrating at a frequency of 200·Hz. Use 340·m/s for the speed of sound in air.
(a) What is the wavelength of the sound waves in the tube? m.
(b) If the 200·Hz vibration respresents the fundamental standing wave for the tube, how long is the tube? m.
(c) If the air in the tube is replaced with a different gas, the frequency of the fundamental standing wave changes to 160·Hz. What is the speed of sound in this new gas? m/s.
To solve this question, we need to understand the concept of thin film interference. Thin film interference occurs when light waves reflect off the top and bottom surfaces of a thin film and interfere with each other. This interference can either be constructive (which results in bright regions) or destructive (which results in dark regions).
In this scenario, the thin film initially reflects no orange light and appears dark. This means that destructive interference occurred, causing the orange light wave to cancel out.
If we double the thickness of the film and illuminate it again with orange light, the phase difference between the waves reflecting off the top and bottom surfaces of the film will change. This change in phase difference can lead to a change in interference.
If the original destructive interference conditions are still met, even with the doubled thickness, then the film will still appear dark. However, if the phase difference now leads to constructive interference, the film will appear bright, strongly reflecting the orange light.
So, the correct answer is: It could be either bright or dark, depending on the film.