Individual hemoglobin molecules act like tiny polarizers: they absorb light more
ID: 1310340 • Letter: I
Question
Individual hemoglobin molecules act like tiny polarizers: they absorb light more strongly in one direction than another. In solution, the molecules are arranged in random directions, so a test tube of hemoglobin solution doesn't reveal this property. In sickle cell disease, the molecules connect into long, rather rigid fibers. In each fiber, the hemoglobin molecules are oriented so that light that hits the fiber with its electric field parallel to the fiber axis is absorbed much less than light whose electric field is perpendicular to the fiber axis. The fibers make polymer domains: regions where the fibers are connected, and appear to radiate from a center.
If you had a radial domain on a thin microscope slide, and it had fibers thickly radiating in all directions from a common center, what would the pattern of transmitted light look like if you placed the slide between polarizers which had been previously crossed to extinguish all light?
Explanation / Answer
The pattern of transmitted light would be radial too, but the center would be offset from the center of the domain on microscope slide by a distance of sin(d/2)*mu
where d is the thickness of slide
mu is the refractive index of medium