Question

An object 3m high i s placed 20cm convex lens of focal of 12cm .find the nature ,position and height of image ?

Answer 1

Answer:

Answer here

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given :-

u=>-20cm

f =>+12cm

h =>3cm

v =>?

h'=>?

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lens is convex ,that's why focal length is +ve

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using lens formula :-

1/v -1/u =>1/f

1/v -1/-20=>1/12

1/v +1/20=>1/12

1/v =>1/30

v=>30cm

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V is also positive ,image is located on other side of lens

m =>v/u

=>+30/-20=>-1.5

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since m is negative a s greater than 1 ,the image is real ,inverted and larger then object

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m =>h'/h

1.5=>h'/3

h'=>-4.5cm

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hope helps uh❤

Answer 2

Given

hight of object = 3m

u = - 20cm

f = 12cm

from lens formula

1/v - 1/u= 1/f

1/v = 1/12 - 1/20

1/v = 8/240

v = 30cm

v = 0.3m

menifecation of lens = -v/u

= -0.3/0.2= hight of image /hight of object

hight of image = -3*3/2 = -4.5m

so the image real and inverted