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When an Object is Placed at a Distance of 50 Cm from a Concave Spherical Mirror, the Magnification Produced Is, `-1/2`. Where Should the Object Be Placed to Get a Magnification Of, `-1/5`? - Science

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प्रश्न

When an object is placed at a distance of 50 cm from a concave spherical mirror, the magnification produced is, `-1/2`. Where should the object be placed to get a magnification of, `-1/5`? 

उत्तर

Given,
Magnification `(m)=-1/2`

Distance of the object (u) = −50 cm
We have to find the distance of the object when the magnification is `=-1/5`
Therefore, using the magnification formula, we get  
`m=-v/u` 
v=-mu 
`v=-(-1/2xx-50) ` 
`v=-25` cm 
Now, using the mirror formula, we get 
`1/f=1/u+1/v` 
`1/f=1/-"mu"+1/u` 
`1/f=1/-25+1/-50` 
or` 1/f=-2/50-1/50=3/-50` 
or `f=-50/3` cm 

Now,
Magnification = `m=-1/5`

Therefore, using the mirror formula, we get 

`1/f=1/-"mu"+1/u` 

`or -3/50=(-5)/-5+1/u` 

`or (-3)/50=5/u+1/u` 

`or (-3)/50 =6/4` 

`u=-50xx6/3=-100` cm  

The object should be placed in front of the mirror at a distance of 100 cm to get the magnefiction of `-1/5` 

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पाठ 4: Reflection of Light - Exercise 5 [पृष्ठ १९९]

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लखमीर सिंह Physics (Science) [English] Class 10
पाठ 4 Reflection of Light
Exercise 5 | Q 27 | पृष्ठ १९९

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संबंधित प्रश्‍न

A student has obtained a point image of a distant object using the given convex lens. To find the focal length of the lens he should measure the distance between the :

(A) lens and the object only

(B) lens and the screen only

(C) object and the image only

(D) lens and the object and also between the object and the image


A student has obtained an image of a distant object on a screen to determine the focal length F1 of the given lens. His teacher, after checking the image, gave him another lens of  focal length F2 and asked him to focus the same object on the same screen. The student found that to obtain a sharp image, he has to move the lens away from the screen. From this finding, we may conclude that both the lenses given to the student were :

(A) Concave and F1 < F2

(B) Convex and F1 < F2

(C) Convex and F1 > F2

(D) Concave and F1 > F2


An object is held 20 cm away from a converging lens of focal length 10 cm. Find the position of the image formed.


Linear magnification produced by a concave mirror may be:

(a) less than 1 or equal to 1
(b) more than 1 or equal than 1
(c) less than 1, more than 1 or equal to 1
(d) less than 1 or more than 1


Draw a diagram to show how a converging lens held close to the eye acts as a magnifying glass. Why is it usual to choose a lens of short focal length for this purpose rather than one of long focal length?


The lens A produces a magnification of, − 0.6 whereas lens B produces a magnification of + 0.6.  

 What is the nature of lens A?


At what distance should an object be placed from a lens of focal length 25 cm to obtain its image on a screen placed on the other side at a distance of 50 cm from the lens? What will be the magnification produced in this case?


At which position will you keep an object in front of a convex lens so as to get a real image of the same size as the object? Draw a figure.


The lens of the eye is flattened when looking at nearby objects.


The image of a candle flame formed by a lens is obtained on a screen placed on the other side of the lens. If the image is three times the size of the flame and the distance between lens and image is 80 cm, at what distance should the candle be placed from the lens? What is the nature of the image at a distance of 80 cm and the lens?


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