Final answer:
The thickness of the ethyl alcohol film needed to reflect only green light (500 nm) strongly can be calculated using the formula for interference in thin films. Based on the given refractive index of 1.36 for ethyl alcohol and the observed color, the thickness is approximately 183.82 nm.
Step-by-step explanation:
The reflection of light by a thin film is caused by interference. When a region of the film reflects only green light (500 nm) strongly, it means that this specific wavelength is experiencing constructive interference. To determine the thickness of the film, we can use the formula:
2nt = mλ
Where:
- n is the refractive index of the film
- t is the thickness of the film
- m is the order of the interference
- λ is the wavelength of the light
In this case, since the film reflects only green light (500 nm), we can set λ = 500 nm. The refractive index of ethyl alcohol is given as n = 1.36. The order of the interference, m, is 1 since the film reflects the light strongly.
Plugging in these values into the formula, we can solve for t:
2(1.36)t = 1(500 nm)
2.72t = 500 nm
t = 500 nm / 2.72
t ≈ 183.82 nm
Therefore, the thickness of the film that reflects only green light strongly is approximately 183.82 nm.