Question

The red light (wavelength = 630 nm) illuminates a cuvette at an incident angle of 30° with respect to the normal. The cuvette is made of glass (refractive index = 1.515) and some protein solution is inside the cuvette. At a specific protein solution, the refractive index of the solution is 1.34.

If the protein concentration is increased, the refractive index of the solution gets higher. What physical parameter (e.g., angular change, distance change) can you measure to detect the increased protein concentration? (This is a technique that scientists use to measure protein concentration.)

Answer 1

We have

n₁sin i=n₂sin r

from snell's law

n₁&n₂ indicate refractive index of medium 1 and 2 respectively and i&r denote angle of incidence and angle of refraction.

Thus on increase in protein concentration refractive index gets higher hence the angle of refraction decreases.