Question

In the figure, a broad beam of light of wavelength 610 nm is incident at 90? on a thin, wedge-shaped film with index of refraction 1.45. An observer intercepting the light transmitted by the film sees 10.0 bright and 9.00 dark fringes along the length of the film. By how much does the film thickness change over this length?

Answer 1

The film thickness changes by 210.34 nm over the given length.

Step-by-step explanation:

For thin film interference, the change in film thickness can be determined using the formula:

Δt = λ / (2 * n * sin(θ))

Where Δt is the change in thickness, λ is the wavelength of light, n is the index of refraction of the film, and θ is the incident angle.

Using the given values, we have:

Δt = (610 nm) / (2 * 1.45 * sin(90°))

Δt = 210.34 nm

Therefore, the film thickness changes by 210.34 nm over the given length.