Normal vision is called 20-20 vision. These numbers are actually a ratio—a comparison of the distance you can see to the distance a normal-sighted person can see. For example, a person with 20-30 vision can see from a distance of 20 feet what a person with 20-20 vision can see from a distance of 30 feet. Based on this knowledge, explain what the following numbers mean regarding vision.
a. 20-100
b. 20-40