Hint: To solve this question we have to know about convex lenses. We know that this lens converges to a straight beam of light. This lens is thicker at the middle and gets more slender as we move towards the edges. Some convex lenses utilized are recorded in the focuses beneath- Amplifying glasses ,Eyeglasses ,Cameras ,Magnifying instruments. We also know that, Magnifying lenses utilize a curved focal point to produce amazingly amplified pictures of little items.
Complete answer:
when the object is at infinity, its image is formed at the focus of the lens. For determination of the focal length of the lens, the distance between the lens and the screen should be measured because all the rays converge at a common point on the screen.
We know that, concave lens is a lens to such an extent that an equal light emission going through it is caused to wander or fan out and this is A lens having at any rate one surface bended like the internal surface of a circle. Convex lens has Positive Focal Length.concave lens has negative focal length.If a sharp image of a distant object is obtained using a convex lens. In order to determine the focal length of a lens, a student needs to measure the distance between the lens and the screen.
So, the right answer is option B.
Note: We know that the main example of this convex lens is the human eye.Another example of this convex lens is magnifying glass.. We have to keep these in mind. Many people can get confused between convex and concave lenses. But a concave lens diverges the straight beam of light.
