 Covering one-half of a convex lens with black paper does not prevent it from forming a complete image of an object. The uncovered half still converges light rays to form an image. However, the image’s brightness and sharpness may be reduced due to the decreased amount of light being focused. Experimentally, this can be observed by shining light through the lens onto a screen. The complete, albeit dimmer, image will still be formed.

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## Introduction to Lens Functionality

Basic Principles of Lenses: A lens, such as a convex lens, works by refracting light rays to converge at a point, forming an image. The entire surface of the lens contributes to this process, bending light rays from different parts of the object.

### Experiment Setup

Testing Image Formation: To experimentally verify the effect of covering half of a convex lens with black paper, one can set up a simple experiment. Place an object in front of the lens and project its image onto a screen, first with the entire lens exposed and then with half covered.

#### Observing with an Uncovered Lens

Full Lens Functionality: Initially, with the entire lens exposed, the lens will form a complete and bright image on the screen. This is due to the full surface of the lens participating in bending the light rays from the object.

##### Covering Half of the Lens

Partial Light Passage: When one-half of the lens is covered with black paper, only half of the lens is available to refract light. This setup tests whether the uncovered portion of the lens is capable of forming a complete image.

###### Observations from the Experiment

Image Formation with Partial Lens: Despite half of the lens being covered, a complete image of the object is still formed on the screen. However, this image may appear less bright and less sharp compared to when the entire lens is used, due to the reduced amount of light being focused.

Understanding Lens Image Formation: This experiment demonstrates that a convex lens can still form a complete image even when partially obstructed. It highlights the principle that each part of a lens can independently contribute to image formation, although the quality of the image is affected by the extent of the lens’s exposure to light.

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Questions of 10th Science Chapter 9 in Detail

 Define the principal focus of a concave mirror. The radius of curvature of a spherical mirror is 20 cm. What is its focal length? Name a mirror that can give an erect and enlarged image of an object. Why do we prefer a convex mirror as a rear-view mirror in vehicles? Find the focal length of a convex mirror whose radius of curvature is 32 cm. A concave mirror produces three times magnified (enlarged) real image of an object placed at 10 cm in front of it. Where is the image located? A ray of light travelling in air enters obliquely into water. Does the light ray bend towards the normal or away from the normal? Why? Light enters from air to glass having refractive index 1.50. What is the speed of light in the glass? Find out, from Table, the medium having highest optical density. Also find the medium with lowest optical density. You are given kerosene, turpentine and water. In which of these does the light travel fastest? The refractive index of diamond is 2.42. What is the meaning of this statement? Define 1 dioptre of power of a lens. A convex lens forms a real and inverted image of a needle at a distance of 50 cm from it. Where is the needle placed in front of the convex lens if the image is equal to the size of the object? Find the power of a concave lens of focal length 2 m. We wish to obtain an erect image of an object, using a concave mirror of focal length 15 cm. What should be the range of distance of the object from the mirror? Name the type of mirror used in the following situations. (a) Headlights of a car. (b) Side/rear-view mirror of a vehicle. (c) Solar furnace. One-half of a convex lens is covered with a black paper. Will this lens produce a complete image of the object? An object 5 cm in length is held 25 cm away from a converging lens of focal length 10 cm. What is the position, size and the nature of the image formed. A concave lens of focal length 15 cm forms an image 10 cm from the lens. How far is the object placed from the lens? An object is placed at a distance of 10 cm from a convex mirror of focal length 15 cm. Find the position and nature of the image. The magnification produced by a plane mirror is +1. What does this mean? An object 5.0 cm in length is placed at a distance of 20 cm in front of a convex mirror of radius of curvature 30 cm. Find the position of the image, its nature and size. An object of size 7.0 cm is placed at 27 cm in front of a concave mirror of focal length 18 cm. At what distance from the mirror should a screen be placed, so that a sharp focussed image can be obtained? Find the focal length of a lens of power – 2.0 D. What type of lens is this? A doctor has prescribed a corrective lens of power +1.5 D. Find the focal length of the lens. Is the prescribed lens diverging or converging?