Properties of the formed images by convex lens and concave lens

Convex lens

The convex lens is a converging lens as it collects the refracted rays , The point of collection of the parallel rays ( produced from the sun or any distant object ) after being refracted from the convex lens is called the focus of the lens ( F ) .

The distance between the focus of the lens and its optical center is called the focal length of the lens ( f ) , The focal length ( f ) = ½ × radius of curvature ( r ) .

We notice that the image formed by the convex lens can be received on the screen as it is a real image formed as a result of collection of the refracted rays .

The piece of paper can be burned by a convex lens because the convex lens can converge and direct the sunlight in a point ( focus ) which is burned .

Convex lens and concave lens

Convex lens and concave lens

If we have thin lens and thick lens , The thin lens has greater focal length than the thick one because the radius of the thin lens is bigger than that of the thick lens .

The light rays after passing through the convex lens

The incident light ray that is parallel to the principal axis , It exits from the lens ( or refracts ) passing through the focus .

The incident light ray that passes through the focus , It exits from the lens parallel to the principal axis .

The incident light ray that passes through the optical center of the lens , it passes through the lens without refraction .

Cases of formation of images by convex lens ( converging lens )

When the position of the object is very far , the position of the image is at the focus , The formed image will be real and very tiny ( dot ) .

When the position of the object is at a distance greater than the double ( twice ) of the focal length , ( after the center of curvature ) , The position of the image is between the focus and the center of curvature , The formed image will be real , diminished ( small ) and inverted .

The position of the object is at the center of curvature ( C ) ( at a distance equals the radius of curvature ) , The position of the image is at the center of curvature , The formed image will be real , inverted and equal to the object .

When the position of the object is between the focus and the center of curvature ( at a distance greater than the focal length but less than radius of curvature , The position of the image is after the center of curvature , The formed image is real , inverted and magnified .

When the position of the object is at the focus , No image is formed as the image is at infinity where the rays penetrate as parallel .

When the position of the object is before the focus , ( at a distance less than the focal length ) , The position of the image is after the position of the object in the same side ( in front of the lens ) , The formed image will be virtual , erect and magnified .

Concave lens

If the convex lens is replaced by a concave lens , the formed image can not be received on the screen , because the incoming rays diverge after refraction .

When the position of the object is in front of the concave lens , The position of the image is before the object in the same side , The image formed by the concave lens is always virtual , erect and small .

The concave lens is known as the diverging lens because it diverges the rays after they pass through it , The image formed by the concave lens is a virtual image because it can not be received on a screen .

You may also like...

8 Responses

  1. Neicy says:

    Dear editor,
    Thank you this article was needed.

  2. sharon says:

    Thanks … its really helpful

  3. Shuaib says:

    Nice website.It is useful to me.

  4. strikingtaurus says:

    very helpful thank u

Leave a Reply

Your email address will not be published. Required fields are marked *