The Following Diagram in Given Below Shows an Object Oa and Its Virtual Image Ib Formed by a Lens. - Physics


The following diagram in given below shows an object OA and its virtual image IB formed by a lens.



(a)The lens is concave lens.
(b)The required diagram is 

(c)The focal length is measured from optical centre C to F2.

Concept: Concave Lens
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Where must the object be placed for the image formed by a converging lens to be: 

 real, inverted and smaller than the object?

What type of image is always made by a concave lens?

Which of the following can form a virtual image which is always smaller than the object?
(a) a plane mirror
(b) a convex lens
(c) a concave lens
(d) a concave mirror

When an object is placed 10 cm in front of lens A, the image is real, inverted, magnified and formed at a great distance. When the same object is placed 10 cm in front of lens B, the image formed is real, inverted and same size as the object. 

 What is the nature of lens B? 

Only one of the following applies to a concave lens. This is:
(a) focal length is positive
(b) image distance can be positive or negative
(c) height of image can be positive or negative
(d) image distance is always negative

State whether the following statement is true or false:
Short-sightedness can be cured by using a concave lens. 

Out of the two lenses, one concave and the other convex, state which one will show the divergent action on a light beam.

Draw a diagram to represent the second focus of a concave lens.

An object is placed on the axis of a lens. An image is formed by refraction in the lens. For all positions of the object on the axis of the lens, the positions of the image are always always between the lens and the object.State three characteristics of the image.

State two applications  a concave lens .

An object of height 4 cm is kept at a distance of 30 cm from a concave lens. Use lens formula to determine the image distance, nature and size of the image formed if focal length of the lens is 15 cm.

If the image formed by a lens is diminished in size and erect, for all positions of the object, what type of lens is it?

Explain the working of an astronomical telescope using refraction of light.


A student obtained clear image of window grills on the screen. But the teacher told him to get the image of a tree far away, instead of window. To get a clear image,  the lens must be ............................

Write the SI unit of focal length of a concave lens.

Draw neat diagram to show the
 Divergent action of concave lens

 Express power of a concave lens of focal length 50 cm with its sign.

A lens always forms an image between the object and the lens. 

name the lens.

A concave lens forms the image of an object kept at a distance 20 cm in front of it, at a distance 10 cm on the side of the object.

What is the nature of the image?

Find the focal length of the lens.

Choose the correct alternative and rewrite the following: 

Inside water, an air bubble behaves ....................

An object is placed at a distance of 60 cm from a concave lens of focal length 30 cm.
(i) Use the lens formula to find the distance of the image from the lens.
(ii) List four characteristics of the image (nature, position, size, erect/inverted) formed by the lens in this case.
(iii) Draw a ray diagram to justify your answer of the part (ii).

Define the principal focus of a concave lens.

Convex lens : converging : : concave lens : _______

Convex magnifying glass is called divergent magnifying glass and concave magnifying glass is called converging magnifying glass.

Identify the device used as a spherical mirror or lens in following case, when the image formed is virtual and erect in case.

Object is placed between infinity and device, image formed is diminished and between focus and optical centre on the same side as that of the object.

Distinguish between Concave lens and Convex Lens.

Distinguish between:

Concave Lens and Convex Lens


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