Lenses and Ray diagrams

what do lenses do

they use the refraction of light rays at an air glass boundary to change the path of the rays

where does the refraction occur?

at the lens axis

how many times would this refraction occur?

twice, once going in and once out, however when doing calculations/drawings this can be ignored and you can assume it’s only once

define principle axis

a line running through the center of the lens and is perpendicular to the lens axis

where does a convex lens bring parallel light rays

to the principle focus or focal point

what is the name of the distance from the lens axis to the focal point

focal length

what does a thicker lens do compared to a thinner one?

bend light through a larger angle (making the focal length smaller) and be more powerful in general

what is the unit for the power of a lens and what is the formula linking it and focal length

Diopter,

P=1/f (where P=power and f=focal length)

what are the steps to drawing a ray diagram?

1. draw rays parallel to the principle axis

2. draw refracted ray passing through the principle focal

3. draw undeviated ray though the middle of the lens

4. draw an arrow to from x-axis where the rays cross

what has to be true for the image to be real or to be able to project it on a screen?

if the image formed is on the opposite side of the lens to the object

what would it be if the image was on the same side as the object

virtual