I’ve dealt with this problem all my life – i have high powered glasses (-6 and – 8, with some cylindrical /spherical tweaks). My glasses work great. But i wore them while swimming in the crystal blue Mediterranean, and when I’m diving in, i realized the glasses aren’t effective. I understand the wavy reflective patterns interrupting, but why cant I focus on anything easily?
In: Physics
The way your glasses work is (very basically) by bending light towards more the front or back of your pupils. Glasses can do this because the refractive index of glass is different from the refractive index of air. The refractive index is how we describe how much light bends as it passes through a transition to different mediums: the bigger the difference, the more it bends. Combined with the shape of the lenses, we can bend the light more towards the point in your eyeball where it is most clearly seen.
Water also has a different refractive index to air, which is why things in a swimming pool can often appear magnified. Water’s refractive index is closer to glass than air’s is, so the difference between their refractive index is smaller, and thus light bends less as it moves from one to the other. This changes where the point the light it bent towards is, thus making your glasses less effective.
Latest Answers