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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)
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(a) Convex Lens
(b) Negative as the image is real and inverted.
(c) `1/"f" = 1/"v" - 1/"u"`
`1/20 = 1/"v" - 1/-20`
`1/"v" = 1/20 - 1/21`
= `(21 - 20)/420`
= `1/420`
v = 420 cm
OR
(c) 
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A 1 cm high object is placed at a distance of 2f from a convex lens. What is the height of the image formed?
Where should an object be placed in order to use a convex lens as a magnifying glass?
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.
Show by a diagram the refraction of two light rays incident parallel to the principal axis on a convex lens by treating it as a combination of a glass slab and two triangular glass prisms.
A lens forms an upright and magnified image of an object. Name the lens.
Out of the five incident rays shown in the figure find the three rays that are obeying the laws of refraction and may be used for locating the position of image formed by a convex lens:
(A) 1, 2 and 3
(B) 2, 3 and 4
(C) 3, 4 and 5
(D) 1, 2 and 4
For finding the focal length of a convex lens by obtaining the image of a distant object, one should use as the object.
(1) a well lit distant tree
(2) window grill in the class room
(3) any distant tree
(4) a lighted candle kept at the other end of the table.
A lens always forms an image between the object and the lens.
A lens always forms an image between the object and the lens.
Can one bum a piece of paper in daylight by just using a convex lens instead of a match or any direct flame? Support your answer with the help of an appropriate ray diagram.
