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प्रश्न
A lens of focal length 20 cm is used to produce a ten times magnified image of a film slide on a screen. How far must the slide be placed from the lens?
उत्तर
Given:
m = -10 (negative sign implies real image)
f = 20 cm
Object distance = -u
Lens formula is given by:
`1/f=1/v-1/u`
Magnification in case of convex lens is given by:
`m=v/-u`
`v=mu`
`v=(-10)xx(-u)=10u`
Putting these values in lens formula, we get:
`1/f=1/v-1/u`
`1/20=1/(10u)+1/u`
`1/20=1+10/(10u)`
`1/20=11/(10u)`
`10u=220`
`u=220/10=22` cm
Thus, object distance = -u = -22 cm
So, the slide is placed at a distance 22 cm from the poles of the lens.
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संबंधित प्रश्न
A student has obtained an image of a well-illuminated distant object on a screen to determine the focal length, F1of the given spherical mirror. The teacher then gave him another mirror of focal length, F2 and asked him to obtain a focused image of the same object on the same screen. The student found that in order to focus the same object using the second mirror, he has to move the mirror away from the screen. From this observation, it may be concluded that both the spherical mirrors given to the student were (select the correct option)
(A) Concave and F1 < F2
(B) Concave and F1 > F2
(C) Convex and F1 < F2
(D) Convex and F1 > F2
The height of the image formed by an object of height 10 cm placed in front of a plane mirror is __________.
(a) 5 cm
(b) 10 cm
(c) 15 cm
(d) 20 cm
Describe the New Cartesian Sigh Convention used in optics. Draw a labelled diagram to illustrate this sign convention.
Write down a formula for the magnification produced by a concave mirror.
in terms of object distance and image distance
When an object is placed at a distance of 36 cm from a convex lens, an image of the same size as the object is formed. What will be the nature of image formed when the object is placed at a distance of:
10 cm from the lens?
What is the nature of the image formed by a convex lens if the magnification produced by the lens is, – 0.5?
Determine how far an object must be placed in front of a converging lens of focal length 10 cm in order to produce an erect (upright) image of linear magnification 4.
To obtain a magnification of, –0.5 with a convex lens, the object should be placed:
(a) at F
(b) between optical centre and F
(c) between F and 2F
(d) beyond 2F
Magnification produced by a rear view mirror fitted in vehicles ______.
A negative sign in the value of magnification indicates that the image is ______.
