Yesh Find Out F1 and F2 of Symmetric Convex Lens Experimentally Then Which Conclusion is True. - Science and Technology 1


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


  • a) 𝐹1 = 𝐹

  • b) 𝐹1 > 𝐹

  • c) 𝐹1 < 𝐹

  • d) 𝐹1 ≠ 𝐹



a) 𝐹1 = 𝐹2  

Concept: Convex Lens
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2018-2019 (March) Balbharati Model Question Paper Set 3


Analyse the following observation table showing variation of image-distance (v) with object-distance (u) in case of a convex lens and answer the questions that follow without doing any calculations : 

S. No. Object-Distance
u (cm)
v (cm)
1 –100 +25
2 –60 +30
3 –40 +40
4 –30 +60
5 –25 +100
6 –15 +120

(a) What is the focal length of the convex lens? Give reason to justify your answer.

(b) Write the serial number of the observation which is not correct. On what basis have you arrived at this conclusion?

(c) Select an appropriate scale and draw a ray diagram for the observation at S.No. 2. Also find the approximate value of magnification.

"A lens can form a magnified erect image as well as magnified inverted image of an object placed in front of it." State the nature of this lens and draw ray diagrams to justify the above statement. Mark the positions of O, F and 2F in the diagram.

A lens forms an upright and diminished image of an object when the object is placed at the focal point of the given lens.

1) Name the lens

2) Draw a ray diagram to show the image formation.

Complete the following table:

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

Describe with the help of a ray diagram the nature, size and position of the image formed when an object is placed at infinity (considerable distance) in front of a convex lens. State three characteristics of the image so formed.

 List some things that convex lens and concave mirror have in common.  

Describe the nature of image formed when an object is placed at a distance of 30 cm from a convex lens of focal length 15 cm.

 What type of images can a convex lens make?

Which causes more bending (or more refraction) of light rays passing through it : a convex lens of long focal length or a convex lens of short focal length?

What type of lens is used to correct  


In a certain murder investigation, it was important to discover whether the victim was long-sighted or short-sighted. How could a detective decide by examining his spectacles?

Study the following diagram :


What are the points O and O’ called?

Study the diagram below.

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

Study the diagram below.

State three characteristics of the image

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

A lens forms an upright and magnified image of an object  name the lens

A teacher sets up the stand carrying a convex lens of focal length 15 cm at 42.7 cm mark on the optical bench. He asks four students A, B, C and D to suggest the position of screen on the optical bench so that a distinct image of a distant tree is obtained almost immediately on it. The positions suggested by the students were as

A. 12.7 cm

B. 29.7 cm

C. 57.7 cm

D. 72.7 cm

The correct position of the screen was suggested by

(a) A

(b) B

(c) C

(d) D

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 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 lens forms the image of an object placed at a distance 15 cm from it, at a distance 60 cm in front of it. Find :  the magnification.

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 ______________.

Point out the difference between a convex lens and a concave lens.

State the position of object, position of image, nature of image when: Convex lens is used as objective lens of photographic camera.

Draw a diagram to show the convergent action of a convex lens by treating it as a combination of glass block and two triangular glass prisms, with the aid of two parallel incident rays.

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.

_______ is a combination of two convex lenses with small focal length.

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.

  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


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