Answer :
Final answer:
The equivalent of a Reduced Snellen 20/50 optotype in metric notation for a working distance of 40 cm is 1M. This calculation requires understanding the Snellen fraction and converting the measurements appropriately to represent visual acuity at the reduced distance. Therefore optionB.1M is correct.
Explanation:
The question asks for the equivalent of a Reduced Snellen 20/50 optotype in metric notation, assuming a working distance of 40 cm. To convert this to metric notation, understanding the Snellen fraction is key. The Snellen fraction, in essence, represents the distance at which a person with normal vision can read the same line as the person being tested. Given the 20/50 standard, it implies that what a person with normal vision can see at 50 feet, a person with 20/50 vision can only see at 20 feet.
However, since we are dealing with a reduced distance of 40 cm (which is approximately the distance one would use for reading or other close work), we need to consider how this translates into a comparable visual acuity measurement in metric units. The key to converting Snellen fractions to metric (meters) involves understanding that 20 feet is roughly equal to 6 meters in metric terms. Therefore, for a Snellen measurement of 20/50 to be equivalent at a 40 cm distance, the metric notation would be in the form of 'X' M at 40 cm, where 'X' would represent the size of the optotype in meters that matches the visual acuity.
After performing the necessary calculations, which involve considering the angular size of the optotype and its visual acuity equivalence at the reduced distance, the answer is 1M (B) for the equivalent metric notation at a 40 cm working distance.
