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What is the focal length of convex lens having power of lens +4D
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Azhar08:
The power of a convex lens is positive and that of a concave lens is negative. Thus a convex lens of focal length 40 cm is said to possess a power of + 2.5 dioptre. similarly the power of a concave lens of focal length 20 cm is 5.0 dioptre
is ur doubt clear now
Is the power negative or positive is it's the focal length??
Or* it's the focal length
focal
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1
Solution==>
Focal length=?
Power of lens=+4D
We know that, P=1/f.....(1)
where, p=power of lens
and f=focal length
By substituting value of P in (1)
4=1/f
4f=1
f=1/4
f=0.25
Therefore,
Focal length of lens is 0.25 cm
Focal length=?
Power of lens=+4D
We know that, P=1/f.....(1)
where, p=power of lens
and f=focal length
By substituting value of P in (1)
4=1/f
4f=1
f=1/4
f=0.25
Therefore,
Focal length of lens is 0.25 cm
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P=1/f......power is equal to one divided by focal length ......i think..
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