Question

(i) Name the Lens LL’
(ii) What are the points O and O' called?
(iii) Complete the diagram.
(iv) Write three characteristics of the image
(v) Write the name of a device which is made of this lens.

Answer 1

Hint:To solve this question we should know about lens. Lens is a piece of glass or other transparent materials with curved sides for concentrating or dispersing light rays. To solve this we should know the properties of lenses like the properties of image formation. So, to try to form the image of the object which is placed behind the lens. By observing the nature of the image we can predict the nature of the lens.

Complete answer:
(i) As the object is placed behind the lens, we observe the ray diagram of the object formed in the lens: the rays passed through the lens and then concentrated . By observing the ray we define it as the nature of a convex lens. Convex lenses are conversing in nature.

(ii) As we know the line is parallel through the lens then it will converge at focus.So, point O and O’ are called “Focus”. O and O’ are called Principal Focus of the lens, which means the point where all the rays parallel to the lens will meet.

(iii) Complete diagram is given below:

(iv) To find the characteristic of an image formed through the lens we observe the image.
If the image is formed above or below the principle axis we can compare the size of the object and image.The image will be formed at infinity which will be real, inverted and highly magnified. Three characteristics of the image:
-Real
-Inverted
-Highly Magnified

(v) To find it we look at our surroundings. Convex lenses are used for making microscopes.

Note: A convex lens is thicker at the centre and thinner at the edges and when the light rays pass through the convex lens, it converges the light rays. The focal length of it is positive. This type of lens is used to correct hyperopia. But a concave lens is thicker at the edges and thinner at the centre and when the light rays pass through it, it disperses the light rays. The focal length of it is negative. This type of lens is used to correct myopia.