Convex Lens - Ray diagram

For a Convex Lens, object can be kept at different positions

Hence, we take different cases

Case 1 - Object is Placed at infinity

In this Case, Object is kept far away from lens (almost at infinite distance)

So, we draw rays parallel to principal axis

Since ray parallel to principal axis passes through the Focus

Both rays meet at focus after refraction

Hence, Image is formed at F ₂

And it is very very small

We can say that

• Image is Real
• Image is Inverted
• Image is Smaller than the Object (Highly Diminished)

Case 2 - Object is beyond 2F

Here, Object AB is beyond 2F ₁

First, we draw a ray parallel to principal axis

So, it passes through focus after refraction

We draw another ray which passes through Optical Center

So, the ray will go through without any deviation

Where both rays meet is point A'

And the image formed is A'B'

This image is formed between F ₂ and 2F ₂

We can say that

• Image is Real
• Image is Inverted
• Image is Smaller than the Object (Diminished)

Case 3 - Object is at 2F

Here, Object AB is at 2F ₁

First, we draw a ray parallel to principal axis

So, it passes through focus after refraction

We draw another ray which passes through Optical Center

So, the ray will go through without any deviation

Where both refracted rays meet is point A'

And the image formed is A'B'

This image is formed at 2F ₂

We can say that

• Image is Real
• Image is Inverted
• Image is exactly the same size as that of Object

Case 4 - Object is between F and 2F

Here, Object AB is kept between F ₁ and 2F ₁

First, we draw a ray parallel to principal axis

So, it passes through focus after refraction

We draw another ray which passes through Optical Center

So, the ray will go through without any deviation

Where both refracted rays meet is point A'

And the image formed is A'B'

This image is formed between beyond 2F ₂

We can say that

• Image is Real
• Image is Inverted
• Image is larger than the object (Magnified)

Case 5 - Object is at F

Here, Object AB is kept at F ₁

First, we draw a ray parallel to principal axis

So, it passes through focus after refraction

We draw another ray which passes through Optical Center

So, the ray will go through without any deviation

We observe that both rays are parallel to each other

Hence we can say that they meet at infinity.

Hence, the rays form an image at infinity

And image formed would be larger than the object

We can say that

• Image is Real
• Image is Inverted
• Image is larger than the object (Magnified)

Case 6 - Object is between O and F

Here, Object AB is kept between O and F ₁

First, we draw a ray parallel to principal axis

So, it passes through focus after refraction

We draw another ray which passes through Optical Center

So, the ray will go through without any deviation

We observe that both refracted rays are diverging

It means that they would have met at some point

Hence, we extend both rays behind the lens

We see that the rays form an image behind the lens (on the left side).

So, the image is virtual

And image formed would be larger than the object

We can say that

• Image is virtual (behind the lens)
• Image is erect
• Image is larger than the object (Magnified)

To summarise