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?

1 answer

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.