What is the angle subtended by the largest letter in the Snellen cha on a person's eye who is reading it from a distance of 6 meters?
1 minute
10 minutes
50 minutes
60 minutes
Ans: C. 50 minutes(Ref: Yanoff & Duker 4/e p42; Parson 22/e p98, 21/e p98-100)The angular spacing between the bars of the C or E in Snellen's cha is 1 minute for the 6/6 letter (smallest letter).The largest letter on the Snellen's cha is the 6/60 letter.When viewed from a distance of 6 meter, this letter subtends an angle of 50 minutes in the eye and the bars of the letter subtend an angle of 10 minutes.