Four students A, B, C and D performed an experiment to determine the focal length of a convex lens by using a lighted candle kept at a considerable distance as the object. They represented the position of image by drawing the following diagrams:

Which diagram describes the correct position of image of the candle?
(1) A
(2) B
(3) C
(4) D

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Solution

A convex lens converges the rays coming from a distant object to form a sharp image on its focus. In order to determine the focal length of the lens, students need to obtain the image of a distant object at the focal point of the lens. So, in the above experiment, the image should form at the focus.

Hence, the correct answer is option 3.

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Similar questions

Q. Four students A, B, C and D performed an experiment to determine the focal length of a concave mirror by using a lighted candle kept at a considerable distance as the object. They represented the position of image by drawing the following diagrams:

Which diagram describes the correct position of the image of the candle?
(1) A
(2) B
(3) C
(4) D

A student focuses the image of a candle flame on a white screen using a convex lens. He noted down the position of the candle screen and the lens as shown below
Position of candle = 12.0 cm
Position of convex lens = 50.0 cm
Position of the screen = 88.0 cm
(i) What is the focal length of the convex lens?
(ii) Where will the image be formed if he shifts the candle towards the lens at a position of 31.0 cm?
(iii) What will be the nature of the image formed if he further shifts the candle towards the lens?
(iv) Draw a ray diagram to show the formation of the image in case (iii) as said above.

Q. A student is performing an experiment to study the formation of image of a lighted candle by a converging lens. The converging lens has a focal length of 25 cm and the candle is placed at a distance of 15 cm from the lens.
(a) State three characteristics of the image of the candle so formed which will be observed by the student.
(b) Name a simple device which works under these conditions.

Q. Rohit focused the image of a candle flame on a white screen using a convex lens.
He noted down the position of the candle, screen, and lens as under:
Position of candle =

26.0

cm
Position of convex lens =

50.0

cm
Position of screen =

74.0

What is the focal length of the convex lens?
Where will the image be formed if he shifts the candle towards the lens at a position of

38

cm?
Draw a ray diagram to show the formation of the image in case (ii) as said above?

Question 38
A student focused the image of a candle flame on a white screen using a convex lens. He noted down the position of the candle screen and the lens as shown below
Position of candle = 12.0 cm
Position of convex lens = 50.0 cm
Position of the screen = 88.0 cm

(i) What is the focal length of the convex lens?
(ii) Where will the image be formed if he shifts the candle towards the lens at a position of 31.0 cm?
(iii) What will be the nature of the image formed if he further shifts the candle towards the lens?
(iv) Draw a ray diagram to show the formation of the image in case (iii) as said above.

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