Just like mirrors are the real-life applications of reflection, lens are the real-life applications of refraction.
When the light passes through a lens, it goes through it and undergoes some amount of refraction.
The optical center is the point at which the vertical axis crosses the principal axis.
There are two focuses. One on either side of the lens. This is because the light can be shinned from either side of the lens.
The focal length is the distance between the focus and the optical center.$^7$
For the sake of convenience, the focus created by a set of parallel light rays on the left side of the lens is focus one($f_1$). The focus created by a set parallel light rays on the right side of the lens is focus two($f_2$).
There are two types of lens:$^{2(12)}$
If the image of a lens is real, it is on the opposite side of the lens and vice versa.
Convex lens or converging lens are lens where it is thicker in the center.$^{2(12)}$
When a set of parallel light rays hit the lens, they converge. This creates a focus.
| Object location | Image location | Image size | Virtual or Real | Orientation |
|---|---|---|---|---|
| Beyond 2F | Between the F and the 2F point on the other side of the lens. | Diminished | Real | Inverted |
| At 2F | At 2F on the other side of the lens | Same size | Real | Inverted |
| Between 2F and F | Beyond 2F on the other side | Enlarged | Real | Inverted |
| At F | No image | |||
| Between F and the optical center | Between 2F and F on the same side | Enlarged | Virtual | Erect |
$^7$
