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Maharashtra State BoardSSC (English Medium) 10th Standard

At which position will you keep an object in front of a convex lens so as to get a real image of the same size as the object? Draw a figure.

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Question

At which position will you keep an object in front of a convex lens so as to get a real image of the same size as the object? Draw a figure.

Diagram
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Solution

When an object is placed at the centre of curvature 2F1 of a convex lens, we will get a real image of the same size as the object.

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Chapter 7: Lenses - Exercise [Page 92]

RELATED QUESTIONS

A converging lens has focal length of 12 cm. Calculate at what distance the object should be placed from the lens so that it forms an image at 48 cm on the other side of the lens.


A student is using a convex lens of focal length 10 cm to study the image formation by a convex lens for the various positions of the object. In one of his observations, he may observe that when the object is placed at a distance of 20 cm from the lens, its image is formed at (select the correct option)

(A) 20 cm on the other side of the lens and is of the same size, real and erect.

(B) 40 cm on the other side of the lens and is magnified, real and inverted.

(C) 20 cm on the other side of the lens and is of the same size, real and inverted.

(D) 20 cm on the other side of the lens and is of the same size, virtual and erect.


The image formed by a spherical mirror is real, inverted and is of magnification −2. If the image is at a distance of 30 cm from the mirror, where is the object placed? Find the focal length of the mirror. List two characteristics of the image formed if the object is moved 10 cm towards the mirror.


A student has obtained a point image of a distant object using the given convex lens. To find the focal length of the lens he should measure the distance between the :

(A) lens and the object only

(B) lens and the screen only

(C) object and the image only

(D) lens and the object and also between the object and the image


At what distance from a concave lens of focal length 20 cm, should a 6 cm tall object be placed so that it forms an image at 15 cm from the lens ? Also determine the size of the image formed.


An object is held 20 cm away from a converging lens of focal length 10 cm. Find the position of the image formed.


The image seen in a plane mirror cannot be formed on a screen. What name is given to this type of image?


What is the difference between a real image and a virtual image? Give one example of each type of image


Linear magnification produced by a concave mirror may be:

(a) less than 1 or equal to 1
(b) more than 1 or equal than 1
(c) less than 1, more than 1 or equal to 1
(d) less than 1 or more than 1


In order to obtain a magnification of −2 (minus 2) with a concave mirror, the object should be placed:

(a) between pole and focus
(b) between focus and centre of curvature
(c) at the centre of curvature
(d) beyond the centre of curvature


If a magnification of, −1 (minus one) is to be obtained by using a converging mirror, then the object has to be placed:

(a) between pole and focus
(b) at the centre of curvature
(c) beyond the centre of curvature
(d) at infinity


In order to obtain a magnification of, −1.5 with a concave mirror of focal length 16 cm, the object will have to be placed at a distance 

(a) between 6 cm and 16 cm
(b) between 32 cm and 16 cm
(c) between 48 cm and 32 cm
(d) beyond 64 cm


Linear magnification (m) produced by a rear view mirror fitted in vehicles:

(a) is equal to one
(b) is less than one
(c) is more than one
(d) can be more less than one depending on the position of object


Draw a ray diagram to show the formation of a virtual magnified image of an object by a convex lens. In your diagram, the position of the object and image with respect to the principal focus should be shown clearly.


The lens A produces a magnification of, −0.6 whereas lens B produces a magnification of + 0.6.

  1. What is the nature of lens A?
  2. What is the nature of lens B?

The lens A produces a magnification of, − 0.6 whereas lens B produces a magnification of + 0.6. 

What is the nature of lens B


A student wants to project the image of a candle flame on a screen 80 cm in front of a mirror by keeping the candle flame at a distance of 20 cm from its pole.

  1. Which type of mirror should the student use?
  2. Find the magnification of the image produced.
  3. Find the distance between the object and its image.
  4. Draw a ray diagram to show the image formation in this case and mark the distance between the object and its image.

The image of a candle flame placed at a distance 36 cm from a spherical lens is formed on a screen placed at a distance of 72 cm from the lens. Identify the type of lens and calculate its focal length. If the height of the flame is 2.5 cm, find the height of its image.


At what distance should an object be placed from a lens of focal length 25 cm to obtain its image on a screen placed on the other side at a distance of 50 cm from the lens? What will be the magnification produced in this case?


Solve the following example.

An object kept 60 cm from a lens gives a virtual image 20 cm in front of the lens. What is the focal length of the lens? Is it a converging lens or diverging lens?


At which position will you keep an object in front of convex lens to get a real image smaller than the object? Draw a figure.


What do you understand by the term magnification?


The lens of the eye is flattened when looking at nearby objects.


Magnification of a convex lens is ______.


The image of a candle flame formed by a lens is obtained on a screen placed on the other side of the lens. If the image is three times the size of the flame and the distance between lens and image is 80 cm, at what distance should the candle be placed from the lens? What is the nature of the image at a distance of 80 cm and the lens?


A lens of focal length 5 cm is being used by Debashree in the laboratory as a magnifying glass. Her least distance of distinct vision is 25 cm.

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  2. She keeps a book at a distance 10 cm from her eyes and tries to read. She is unable to read. What is the reason for this?

Ravi kept a book at a distance of 10 cm from the eyes of his friend Hari. Hari is not able to read anything written in the book. Give reasons for this?


The magnification produced when an object is placed at a distance of 20 cm from a spherical mirror is +1/2. Where should the object be placed to reduce the magnification to +1/3.


The focal length of a concave lens is 20 cm. At what distance from the lens should a 5 cm tall object be placed so that its image is formed at a distance of 15 cm from the lens? Also calculate the size of the image formed.


The magnification by a lens is -3. Name the lens and state how are u and v related?


Write an expression for magnification for a lens, explaining the meaning of the symbols used.


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