Glasses, more than meets the eye

As many of you know, I wear glasses because I am nearsighted, meaning I cannot easily see objects that are far away. In order to correct this, I wear glasses that help to bring faraway images to a focus at the retina in the back of my eye, so my brain can receive and interpret them with maximum clarity. Because I am nearsighted, I see images at twenty feet that other people can see at say fifty or sixty feet (I'm not quite sure what my prescription is) away. When images enter my eye they are created at some distance in front of my retina whereas images in the eyes of farsighted people are focused behind the retina. In order to move the focus of images in my eye backward, I need to wear diverging lenses that cause incoming light rays to intersect at a point farther from the source as they diverge (get farther apart by refraction) while coming through the lens, thus they do not meet until they reach a father back location. On the other hand, if I were farsighted, I would have to wear converging lenses that cause rays to intersect closer after leaving the lens as they in a way push the rays of light closer as they are refracted at a smaller angle as they go through the lens.

Transformer

There are many transformers in my neighborhood as I suspect is the same in any neighborhood. Without these transformers our homes would not get the power that they need and nothing electrical would work. The need for transformers is due to the fact that power comes from the plant through electrical lines at very high voltages, into the tens of thousands! Most household appliances, however, operate on only a few hundred volts. So, there needs to be a way to reduce the power from its high voltage to a more usable voltage. This is where a transformer helps. Inside a transformer there are many coils, but lets just focus on two for the general concept. The two coils are separated by an iron core and as the full high voltage from the plant comes into the first coil a magnetic field is generated through the iron to the second coil and an emf is induced. This in turn creates a current in the second coil and this passes through a resistor and the emf becomes what is necessary for the resistor. The number of coils in the first and second coils also varies. The equation V1/V2=N1/N2 shows this as V is the emf and N is the number of loops, showing that the emf decreases proportionally to the number of loops on each side of the transformer.