Convex and concave, hyperopia and myopia
How do you remember which is which?
To recap, convex lenses are used for hyperopia and concave lenses are used for myopia.
An easy way to remember this is:
Sight short (is great)
Focus short
Word short (myopia)
Have you noticed that the lenses used to correct this are also short in the middle? So –
Concave lenses are used to correct myopia.
So we get
Sight short (is great)
Focus short
Word short
Lens short (in the middle = concave)
And likewise
Sight long (is great)
Focus long
Word long (hyperopia)
have you noticed too that the lenses used to correct this are also long in the middle? So –
Convex lenses are used to correct hyperopia.
So we get:
Sight long (is great)
Focus long
Word long
Lens long (in the middle = convex)
