To find the image-distance for varying object-distances in case of a convex lens, a student obtains on a screen a sharp image of a bright object placed very far from the lens. After that he gradually moves the object towards the lens and each time focuses its image of the screen. - Science

Advertisements
Advertisements

To find the image-distance for varying object-distances in case of a convex lens, a student obtains on a screen a sharp image of a bright object placed very far from the lens. After that he gradually moves the object towards the lens and each time focuses its image of the screen.

(a) In which direction – towards or away from the lens, does he move the screen to focus the object?

(b) What happens to the size of image – does it increase or decrease?

(c) What happen when he moves the object very close to the lens?

Advertisements

Solution

(a) As the student moves the object towards the lens, the position of the image shifts away from the lens. To obtain a sharp image, he should move the screen away from the lens.

(b) The size of the image increases when the object is moved near the lens.

(c) When the object is placed very close to the lens, it can be considered to be placed between the focus and the optical centre. In this case, the image formed is virtual, erect and enlarged.

Concept: Convex Lens
  Is there an error in this question or solution?
2014-2015 (March) Delhi Set 1

Video TutorialsVIEW ALL [1]

RELATED QUESTIONS

(a) Draw a ray diagram to show the formation of an image by a convex lens when an object is placed in front of the lens between its optical centre and principal focus.

(b) In the above ray diagram, mark the object distance (u) and the image distance (v) with their proper signs (+ve or –ve as per the new Cartesian sign convention) and state how these distances are related to the focal length (f) of the convex lens in this case.

(c) Find the power of a convex lens which forms a real and inverted image of magnification –1 of an object placed at a distance of 20 cm from its optical centre.


Complete the following table:

Instrument Number of Convex
Lenses
Use
Simple Microscope .............. ..............
Compound Microscope .............. ..............
Telescope .............. ..............

A beam of light travelling in air is incident of water. Draw a ray-diagram indicating the change in its path in water.


Where should an object be placed in order to use a convex lens as a magnifying glass? 


Define principal axis, principal focus and focal length of a convex lens.


 What type of lens is shown in the diagram on the right? What will happen to the parallel rays of light? Show by completing the ray diagram.


A convex lens of focal length 8 cm forms a real image of the same size as the object. The distance between object and its image will be:

(a) 8 cm
(b) 16 cm
(c) 24 cm
(d) 32 cm


An object 2 cm tall is placed on the axis of a convex lens of focal length 5 cm at a distance of 10 m from the optical centre of the lens. Find the nature, position and size of the image formed. Which case of image formation by convex lenses is illustrated by this example? 


A convex lens of focal length 0.10 m is used to form a magnified image of an object of height 5 mm placed at a distance of 0.08 m from the lens. Calculate the position, nature and size of the image. 


Define the term principal axis of a lens.


Define the term principal foci of a convex lens and illustrate your answer with the aid of proper diagrams.


Study the following  diagram : 

Complete the diagram to form the image of the object AB.


A converging lens forms the image of an object placed in front of it, beyond 2F2 of the lens.

Draw a ray diagram to show the formation of image.


A convex lens forms an image of an object equal to the size of the object.state two more characteristics of the image.


State two applications of a convex lens.


Distinguish between:

Concave lens and Convex lens


i. Which type of microscope has the arrangement of lenses shown in the  adjoining figure?
ii. Label the figure correctly.
iii. Write the working of this microscope.
iv. Where does this microscope used?
v. Suggest a way to increase the efficiency of this microscope.


The image obtained while finding the focal length of convex lens is ....................


Observe the following figure and answer the questions.

a) Which optical instrument shows arrangement of lenses as shown in the figure?
b) Write in brief the working of this optical instrument.
c) How can we get different magnifications in this optical instrument?
d) Draw the figure again and labelled it properly


Yesh find out F1 and F2 of symmetric convex lens experimentally then which conclusion is true.


Observe the following figure and complete the table:

Points Answer
(i) Position of the object  
(ii) Position of the image  
(iii) Size of the image   
(iv) Nature of the image  

A convex lens forms an inverted image of size same as that of the object which is placed at a distance 60 cm in front of the lens. Find : The focal length of the lens


If an object is placed in front of a convex lens beyond 2F1, then what will be the position, relative size, and nature of an image which is formed? Explain with a ray diagram.


Rewrite the following statement by selecting the correct option:
The power of a convex lens is 2.5 dioptres. Its focal length is ______________.

Where should an object be placed in front of a convex lens so as to form an inverted and enlarged image? Will the image be real or virtual? Draw a ray diagram to illustrate your answer.


We can burn a piece of paper by focussing the sun rays by using a particular type of lens. Name the type of lens used for the above purpose. Draw a ray diagram to support your answer.


Define the principal focus of a convex lens.


For a specific glass lens f = 0.5 m. This is the only information given to the student. Which type of lens is given to him and what is its power?


_______ times larger images can be obtained by using a simple microscope.


Object at 2F1 of a convex lens : Image at 2F2 : : Object at F1 : _______


Simple microscope : Number of convex lens one : : compound microscope : _______


: Object near the lens : : ______ :


Find the odd one out and give its explanation.


Find the odd one out and give its explanation.


Write the name.

The lens used in simple microscope.


Write scientific reason.

Adults need bifocal lens spectacle.


Observe the given figure and answer the following questions.

  1. Where is the above type of lens construction used?
  2. What type of image is formed by an objective lens?
  3. What happens instead of placing at Fo if the object is placed in between O and Fo?

Differentiate convex lens and concave lens.


Convex lens is also known as ______.


  1. In which type of microscope do you find the lens arrangement as shown in the following diagram?
  2. Write about the working and the use of this microscope.

Distinguish between Concave lens and Convex lens.


Distinguish between:

Concave lens and Convex Lens


Distinguish between Concave lens and Convex Lens.


Distinguish between:

Concave lens and Convex Lens


Distinguish between:

Concave lens and Convex Lens


Share
Notifications



      Forgot password?
Use app×