Advertisements
Advertisements
प्रश्न
Object at 2F1 of a convex lens : Image at 2F2 : : Object at F1 : _______
Advertisements
उत्तर
Object at 2F1 of a convex lens : Image at 2F2 : : Object at F1 : Image at infinity
APPEARS IN
संबंधित प्रश्न
A student is using a convex lens of focal length 18 cm to study the image formation by it for the various positions of the object. He observes that when he places the object at 27 cm, the location of the image is at 54 cm on the other side of the lens. Identify from the following diagram the three rays that are obeying the laws of refraction and may be used to draw the corresponding ray diagram.
(A) 1, 2 and 4
(B) 1, 3 and 5
(C) 2, 4 and 5
(D) 2, 3 and 4
A student wants to project the image of a candle flame on the walls of school laboratory by using a lens:-
(a) Which type of lens should be use and why?
(b) At what distance in terms of focal length 'F' of the lens should be place the candle flame so as to get (i) a magnified, and (ii) a diminished image respectively on the wall?
(c) Draw ray diagram to show the formation of the image in each case?
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) |
Image-Distance 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.
When a ray of light enters from one medium to another having different optical densities it bends. Why does this phenomenon occur?
The diagram given alongside shows a ray of light entering a rectangular block of glass.
(a) Copy the diagram and draw the normal at the point of entry.
(b) Draw the approximate path of the ray of light through the glass block and out of the other side.
For what position of an object a real, diminished image is formed by a convex lens?
Distinguish between a convex lens and concave lens. Which of the two is a converging lens : convex lens of concave lens?
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?
What would be the diameter of the image of the flower on the film?
The focal length of a thin convex lens is ______ than that of a thick convex lens.
A lens forms an erect, magnified, and virtual image of an object. Name the type of lens.
A convex lens forms an image of an object equal to the size of the object. Draw a diagram to illustrate it.
A lens forms an upright and magnified image of an object State whether the image is real or virtual
In the following cases, where must an object be placed in front of a convex lens so that the image formed is upright and enlarged?
Complete the following table:
| Type of lens | Position of object | Nature of image | Size of image |
| Convex | Between optical centre and focus | ||
| Convex | At focus | ||
| Concave | At infinity | ||
| Concave | At any distance |
(a) What type of a lens can be used as a magnifying glass?
(b) Show by a ray diagram the formation of a real image by simple magnifying lens.
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.
Define the terms principal foci and focal lengths as applied to a convex lens, and show them with the help of proper diagrams.
_______ is a combination of two convex lenses with small focal length.
