Formation of Image in a Convex Mirror and Lens

Formation of Image in a Convex Mirror

When the Object is between Infinity and the Pole

The image is

• Formed between the pole and the focus

• Erect

• Diminished

• Virtual

When the Object is at Infinity

The image is

• Formed at the focus

• Extremely diminished

• Virtual

• Erect

Formation of Image by a Convex Lens

1. When the Object is Placed between F₁ and O:

Formation of Image by a Convex Lens
The image is -

• Formed on the same side of the lens

• Virtual

• Erect

• Magnified

2. When the Object is Placed between the Optical Center (O) and first Focus (F₁)

Here we consider two rays starting from the top of the object placed at F₁ and optical center. The ray parallel to the principal axis after refraction passes through the focus (F₂). The ray passing through the optical center goes through the lens undeviated. These refracted rays appear to meet only when produced backwards. Thus, when an object is placed between F₁ and O of a convex lens, a virtual, erect and magnified image of the object is formed on the same side of the lens as the object.

3. When the Object is Placed at 2F₁

The image is -

• Formed at 2F₂

• Real

• Inverted

• Same size as the object

Here one of the rays starting from the top of the object placed at 2F₁ passes through the optic center without any deviation and the other ray which is parallel to the principal axis after refraction passes through the focus. These two refracted rays meet at 2F₂. Thus, when an object is placed at 2F₁ of a convex lens, inverted and real image of the same size as the object is formed at 2F₂ on the other side of the lens.

4. When the Object is Placed between F₁ and F₂

The image is

• Formed beyond 2F₂

• Real

• Inverted

• Magnified

Let us consider two rays coming from the object. The ray which is parallel to the principal axis after refraction passes through the lens and passes through F₂ on the other side of the lens. The ray passing through the optic center comes out of the lens without any deviation. The two refracted rays intersect each other at a point beyond 2F₂. So, when an object is placed between F₁ and 2F₁ of a convex lens the image is formed beyond 2F₂.

5. When the Object is Placed at F₁

The image is -

• Formed at infinity

• real

• Inverted

• Magnified

Here again we consider two rays coming from the top of the object. One of the rays which is parallel to the principal axis after refraction passes through F₂ and the other ray which passes through the optical center comes out without any deviation. These two refracted rays are parallel to each other and parallel rays meet only at infinity. Thus, when an object is placed at F₁ of a convex lens, the image is formed at infinity and it is inverted, real and magnified.

6. When the Object is Placed beyond 2F₁

The image is -

• Formed between F₂ and 2F₂

• Real

• Inverted

• Diminished

The ray parallel to the principal axis after refraction passes through F₂ and the ray which passes through the optical center comes out without any deviation. The refracted rays intersect at a point between F₂ and 2F₂. The image is inverted, real and diminished.

7. When the Object is Placed at Infinity

The image is -

• Formed at F₂

• Inverted

• Real

• Highly diminished

When the object is at infinity, the rays coming from it are parallel to each other. Let one of the parallel rays pass through the focus F₁ and the other ray pass through the optical center. The ray which passes through F₁ becomes parallel to the principal axis after refraction and the ray which passes through the optical center does not suffer any deviation.