Two closely spaced parallel glass plates are separated by 850 nm.What wavelength light source in the visible region (390 nm to 710 nm)will experience maximum transmission through the two plates?
A) 425 nm
B) 489 nm
C) 422 nm
D) 512 nm
E) 474 nm

Question

Two closely spaced parallel glass plates are separated by 850 nm.What wavelength light source in the visible region (390 nm to 710 nm)will experience maximum transmission through the two plates?
A) 425 nm
B) 489 nm
C) 422 nm
D) 512 nm
E) ​474 nm

Quizplus · Accepted Answer

The condition for maximum transmission (constructive interference) in thin film interference is when the path difference is an integer multiple of the wavelength. For two closely spaced plates, this occurs when the wavelength is twice the separation distance. Here, 2 * 850 nm = 1700 nm, which is not in the visible range. However, the closest visible wavelength that is a sub-multiple of 1700 nm is 425 nm (1700/4), which is option A.

Two Closely Spaced Parallel Glass Plates Are Separated by 850