What is the size of the image formed by a convex lens when the object is placed at focus F1?

Spherical lenses are lenses formed by connecting two spherical transparent surfaces. In general, there are two types of spherical lenses. So, lenses formed by binding two spherical surfaces bulging outward are known as convex lenses, while the lenses formed by binding two spherical surfaces such that they are curved inward are known as concave lenses. This is one of the basic difference between concave and convex lenses.

Convex lenses are also known as converging lenses since the rays converge after falling on the convex lens. The concave lenses are known as diverging lenses, as the rays diverge after falling on the concave lens. In this article, we will learn about image formation by concave and convex lenses.

When a ray strikes concave or convex lenses obliquely at its optical centre, it continues to follow its path.
When a ray, parallel to the principal axis strikes concave or convex lenses, the reflected ray passes through a focus on the principal axis.
When a ray, passing through focus strikes concave or convex lenses, the reflected ray will pass parallel to the principal axis.

- When an object is placed at infinity, the real image is formed at the focus. The size of the image is highly diminished and point size.

- When an object is placed beyond the centre of curvature, the real image is formed between the centre of curvature and focus. The image size will not be the same as the object. It will be diminished in size..

- When an object is at the centre of curvature, the real image is formed at the other centre of curvature. The size of the image is the same as compared to that of the object.

- When an object is placed in between the centre of curvature and focus, the real image is formed behind the centre of curvature. The size of the image is larger than that of the object.

- When an object is placed at the focus, a real image is formed at infinity. The size of the image is much larger than that of the object.

- When an object is placed in between focus and optical centre, a virtual image is formed. The size of the image is larger than that of the object.

- When an object is placed at infinity, a virtual image is formed at the focus. The size of the image is highly diminished and point size.

- When an object is placed at a finite distance from the lens, a virtual image is formed between the optical centre and the focus of the convex lens. The size of the image is smaller than that of the object.

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Option 2 : inverted and enlarged

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The correct answer is inverted and enlarged.

Concept:

Convex lens:

A convex lens is thicker at the center than at the edges.
It is called a converging lens because the rays of light that pass through it are brought closer together (they converge).
When parallel rays of light pass through a convex lens the refracted rays converge at one point called the principal focus.
The distance between the principal focus and the center of the lens is called the focal length.
A double convex lens has two foci F1 and F2 and two centers of curvature 2F1 and 2F2.

Explanation:

When the object is between F1 and 2F1:

An enlarged, real and inverted image is formed beyond the center of curvature, 2F2 when an object is placed between the center of curvature, 2F1, and principal focus, F1 of a convex lens.

Additional Information All six cases of image formation by the convex lens:

Object position	Image position	Nature of image	Size of image
At infinity	At F2	Real and inverted	Point sized
Beyond 2F1	Between F2 and 2F2	Real and inverted	Diminished
At 2F1	At 2F1	Real and inverted	Same size
Between F1 and 2F1	Beyond 2F2	Real and inverted	Magnified
At F1	At infinity	Real and inverted	Highly magnified
Between F1 and O	on the same side of the object	Virtual and erect	Magnified