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Question
: Object near the lens : : ______ : 
Solution
: Object near the lens : : Object at focus :
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RELATED QUESTIONS
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) Draw a ray diagram to show the formation of image by a concave lens when an object is placed in front of it.
(b) In the above 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 concave lens in the case.
(c) Find the nature and power of a lens which forms a real and inverted image of magnification –1 at a distance of 40 cm from the optical centre.
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An object 5 cm is placed at a distance of 20 cm in front of a convex mirror of radius of curvature 30 cm. Find the position, nature and size of the image.
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(a)
(b)
(c)
(d)
An object is placed at a distance of 15 cm from a concave lens of focal length 30 cm. List four characteristics (nature, position, etc.) of the image formed by the lens.
An object of height 4.0 cm is placed at a distance of 30 cm from the optical centre 'O' of a convex lens of focal length 20 cm. Draw a ray diagram to find the position and size of the image formed. Mark optical centre 'O' and principal focus 'F' on the diagram. Also find the approximate ratio of size of the image to the size of the object.
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(a) 15 cm
(b) 7 cm
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In order to obtain a real image twice the size of the object with a convex lens of focal length 15 cm, the object distance should be:
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A convex lens produces an inverted image magnified three times of an object placed at a distance of 15 cm from it. Calculate focal length of the lens.
If the object is moved to a point only 3 cm away from the lens, what is the new position, height and nature of the image?
A student did an experiment with a convex lens. He put an object at different distances 25 cm, 30 cm, 40 cm, 60 cm and 120 cm from the lens. In each case he measured the distance of the image from the lens. His results were 100 cm, 24 cm, 60 cm, 30 cm and 40 cm, respectively. Unfortunately his results are written in wrong order.
What would be the image distance if the object distance was 90 cm?
A beam of parallel light rays is incident through the holes on one side of a box and emerges out through the holes on its opposite side as shown in the diagram below:
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- Name a device in which this action of lens is used.
Study the diagram below.
what are the points O, O’ called?
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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
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iii. Write the working of this microscope.
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Define the principal focus of a convex lens.
_______ is a combination of two convex lenses with small focal length.
Object at 2F1 of a convex lens : Image at 2F2 : : Object at F1 : _______
Write the name.
The lens used in simple microscope.
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The above images are that of a specialized slide projector. Slides are small transparencies mounted in sturdy frames ideally suited to magnification and projection since they have a very high resolution and a high image quality. There is a tray where the slides are to be put into a particular orientation so that the viewers can see the enlarged erect images of the transparent slides. This means that the slides will have to be inserted upside down in the projector tray.
To show her students the images of insects that she investigated in the lab, Mrs. Iyer brought a slide projector. Her slide projector produced 500 times enlarged and inverted image of a slide on a screen 10 m away.
a. Based on the text and data given in the above paragraph, what kind of lens must the slide projector have?
b. If v is the symbol used for image distance and u for object distance then with one reason state what will be the sign for `"ЁЭСг"/"ЁЭСв"` in the given case?
c. A slide projector has a convex lens with a focal length of 20 cm. The slide is placed upside down 21 cm from the lens. How far away should the screen be placed from the slide projector’s lens so that the slide is in focus?
OR
c. When a slide is placed 15 cm behind the lens in the projector, an image is formed 3 m in front of the lens. If the focal length of the lens is 14 cm, draw a ray diagram to show image formation. (not to scale)
