For the logarithm of 50, the answer will be 1.x. With the slide rule bezel lined up with 10 at 12 o’clock, 50 on the bezel will be around 42 minutes, which is .7. So the logarithm will be 1.7. Snellen Chart TestThe Snellen chart test is the most common method for measuring visual acuity. During the test, you stand 20 feet away from the chart and cover one eye while reading the smallest line of letters you can see. The results are written as a fraction, such as 20/20, which indicates normal