You can see various objects, observe the various phenomenon and can read various texts using your eyes.

The light gets reflected from objects and our eyes process those light.

And coming light rays form an image on the retina that is the screen of our eye.

And coming light rays form an image on the retina that is the screen of our eye.

And coming light rays form an image on the retina that is the screen of our eye.

So, to form an image from the lens the light rays should be pass through it.

And whenever these light rays are intersected they will form an image.

So, we can say that our eye works as a lens with variable focal length.

Our eyes work as lenses in quite a similar way by choosing various points from an object.

And passing through it's lens to make rays intersect and construct an image on retina.

So now let's discuss about lenses and it's formula in detail.

Lenses and Ray Tracing.

A thin lens is defined as one with a thickness that allows rays to refract, as illustrated in the image.

Let's consider an object some distance away from a converging lens, as shown in the image.

And to find the location and size of the image we will draw the ray diagram .

The formation of image$(A_{â€²}B_{â€²})$ of the object (AB) is shown as,

The image will only form when two or more than two rays intersect with each other.

To, obtain numerical information, we use a pair of equations that can be derived from geometrical analysis of ray for thin lenses.

Therefore, we could write thin lens formula as shown in figure. This is known as Gaussian form of thin lens formula.

There is another form of this formula that is called the Newtonian's formula for thin lens.

So, let's study the newton's Formula for a thin lens.

Newton's formula can be obtained by considering the distance from the object to the first focal point and the distance from the second focal point to the image as shown in the figure.

Starting with the thin lens formula we could note that the above image is true for our example.

Make these substitutions in the thin lens formula and solve for $f$ to obtain the above equation.

Hence, the Newtonian form of the thin lens equation is,

Revision.

An image is formed when the light rays originating from objects passes through a lens and when those rays intersect each other image gets formed.