Math, asked by KyokoHori, 3 months ago

How do I find the focal length?

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Answered by atreyaaavs

Answer:

Focal Length = 15cm

ImageDistance(v)When The Object Is Placed 20cm Towards The lens = 30cm infront of the lens.

Step-by-step explanation:

m = -1(Forms Real Image,Convex Lens).

m=v/u

Therefore,v = -u.

Given,

-u+v = 60cm (-u because of convex lens)

-u-u=60

u=-30cm

By lens formula,

1/f=1/v-1/u

1/f=1/30+1/30

1/f=2/30

f=30/2 = 15cm.

If The object is moved towards the lens by 20cm

u = (-30+20) = -10cm.

By lens formula,

1/f=1/v-1/u

1/v=1/15-1/10

1/v=-1/30

v=-30cm

Here, Image Distance is Negative Because The Object Is placed Between The Focus And The Lens.Eventhough, In sign convention for convex lens the image dstance will be positive.

There is a special case of convex lens which can produce virtual,erect and magnified image when the object is placed between focus and the lens.

Thank You For Reading My Answer!

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