What physical characteristic does a retinal scan biometric device measure?

A.
The amount of light reaching the retina

B.
The amount of light reflected by the retina

C.
The pattern of light receptors at the back of the eye

D.
The pattern of blood vessels at the back of the eye

Explanation:
A retinal scan is a biometric technique that uses the unique patterns on a person’s retina blood vessels.
The human retina is a thin tissue composed of neural cells that is located in the posterior portion of the eye.Because of the complex structure of the capillaries that supply the retina with blood, each person’s retina is
unique. The network of blood vessels in the retina is not entirely genetically determined and thus even identical
twins do not share a similar pattern.
Although retinal patterns may be altered in cases of diabetes, glaucoma or retinal degenerative disorders, the
retina typically remains unchanged from birth until death. Due to its unique and unchanging nature, the retina
appears to be the most precise and reliable biometric, aside from DNA. The National Center for State Courts
estimate that retinal scanning has an error rate of one in ten million.
A retinal scan is performed by casting an unperceived beam of low-energy infrared light into a person’s eye as
they look through the scanner’s eyepiece. This beam of light traces a standardized path on the retina. Because
retinal blood vessels absorb light more readily than the surrounding tissue, the amount of reflection varies
during the scan. The pattern of variations is digitized and stored in a database.
Incorrect Answers:
A: A retinal scan does not measure the amount of light reaching the retina. Therefore, this answer is incorrect.
B: A retinal scan does not measure the amount of light reflected by the retina. Therefore, this answer is
incorrect.
C: A retinal scan does not measure the pattern of light receptors at the back of the eye. Therefore, this answer
is incorrect.

https://en.wikipedia.org/wiki/Retinal_scan