does spectacles really correct eye defects and how?

Answer 1

Yes, they do, in term that they may enable your defect eyes can see clearly (but they never make your eyes turn normal!).

There are some types of eye defects:
1. Cannot see distant objects.
2. Cannot see near object, e.g. newspaper they are reading.
3. Cannot see both distant and near objects.
4. Presbyopia

Basically, all images we receive from our eyes should fall on a part called retina. Defects on the eye make images fall on the wrong area, or make images distorted. Spectacles correct this by making images received correctly on our retinas. Thus, we can see the world clearly.

Answer 2

1

Answer 3

they correct errors of refraction,depends on how much the error is ,and is measured in diopters,they make the image percepted exactly on the retina like ppl with no error

Answer 4

it bends light rays so they focus on the correct part of the retina so you can see clearly.