An object is placed at distance of 30cm from convex mirror. The magnification is 1/2. Where should be the object placed to get magnification 1/3?
Answers
The object should be placed 10 cm far from the focal length of convex mirror to get 1/3 of magnification.
Answer:
MIRROR : It is a shiny polished glass which reflects most of the rays of light falling upon it.
TYPES OF IMAGE FORMED BY IT : Real and Virtual.
TYPES OF MIRROR : Plain mirror and Spherical mirror.
SPHERICAL MIRROR having 2 types of MIRRORS : Concave and Convex mirrors.
CONVEX MIRROR :
Spherical mirror with reflecting surface curved outwards is called convex mirror.
Used as rear view mirror in vehicles because it gives erect image. It helps the driver to view large area.
SIGN CONVENTIONS FOR CONVEX MIRROR :
1. Object distance " u " = ₋ve
2. Image distance " v " = always + ve
3. Focal Length " f " = + ve
4. Height of virtual image = +ve
5. Height of real image = ₋ve
⇒
Given in the question that :
( object distance ) u = ₋ 30cm
( Magnification produced ) m = 1/2
Using the formula, m = ₋v/u ( For a convex spherical mirror )
∴ 1/2 = ₋v/₋30
v = + 15cm.
Now, Using mirror formula, 1/f = 1/v + 1/u
1/f = 1/15 + 1/₋ 30 = 1/30
∴ f = + 30cm
Again, m' = ₋ v'/u'
1/3 = ₋ v'/u'
v' = ₋ u'/3
Using again the mirror formula, 1/f = 1/v' + 1/u'
1/30 = ₋ 3/u' + 1/u' = ₋2/u'
→ u' = ₋ 60cm
Hence, the object should be placed at a distance of 60cm in front of a convex to get the magnification of 1/3.
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