Answer:
n = 1.45
Explanation:
Given:
- Diameter of the dish d = 0.2 m
- Volume per drop V/drop = 0.5 uL
- wavelength of incident light λ = 600 nm
- minimum intensity @ 13 drops
- refractive index of oil : n
Find:
What is the index of refraction of the oil?
Solution:
- Destructive interference can be seen @ 13 drops. So we will use the relation of destructive interference:
n = m*λ / 2*t
- Compute the thickness of the film.
Volume of film = 0.5*13*10^-9 = 6.5*10^-9 m^3
Volume of cylinder = pi*d^2 / 4 * t
pi*d^2 / 4 * t = 6.5*10^-9 m^3
t = 4*(6.5*10^-9 )/ pi*0.2^2 = 2.069*10^-7 m
- Use the given relation @ m = 1:
n = λ / 2*t
n = (600*10^-9) / 2*2.069*10^-7
n = 1.45
