Name: Braille System
Uploaded: 2019-07-19
Duration: 3 min 28 s
Description: What is the Braille system? This video enables students to understand the history behind the Braille system and its importance for visually challenged people.

Question

As an object is slowly brought from infinity to the focus of a convex lens, the image travels from the focus to infinity.' Show this with the help of diagrams with five different positions of the object.

Accepted Answer

The image formed by a convex lens varies in size, position and nature (erect or inverted, real or virtual) depending upon the distance of the object from the lens.

Object very far off (or at infinity): The rays of light coming from an object that is very far off (like the sun) are parallel to each other. We have already seen that if the rays are parallel to the principal axis, they meet at the focus. Thus, the image is formed at the focus. If the rays are not parallel to the principal axis, the image is still formed at the focus. It is real, inverted and smaller than the object.

An object beyond 2F: The image formed is between F and 2F on the other side of the lens. It is real, inverted and smaller than the object. Being a real image it can be formed on a screen placed at that point.

Object at 2F: The image is real, inverted and of the same size as the object. It is located at 2F on the other side of the lens.

The object between F and 2F: The image is real, inverted and larger than the object. It is situated beyond 2F on the other side of the lens.

Object at F: In this case, the refracted rays emerge parallel to each other. Therefore, no image is formed as the rays do not meet. However, since parallel rays are assumed to meet at infinity, we say that the image is formed at infinity. The image formed is real and inverted. It is highly enlarged in size than the object.

The object between F and 0: In this case, the incident rays diverge after refraction. Thus, a real image is not formed. If the divergent rays are produced backwards they meet at a point. Thus, the rays appear to come from this point. The image is, therefore, virtual. It is erect, bigger than the object and is formed on the same side of the lens as the object. When a convex lens is used as a magnifying glass, we keep the object to be viewed between F and 0 of the lens.

As an object is slowly brought from infinity to the focus of a convex lens, the image travels from the focus to infinity.' Show this with the help of diagrams with five different positions of the object.

Important Questions on Refraction and Dispersion of Light

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