Question

frnds help me ....
i m totaly confused in numericals ....

Answer 1

Hey friend!!!! Here's your answer!!♥️

Given: a concave lens of focal length 15cm

Distance of image from lens (v)=10cm

To find: distance of object from lens(u)

We know the formula: 1/v - 1/u= 1/f

Since we have v and f we can substitute their value inthe formula

That is :1/15-1/10= -1/u

1/u=1/30

Therefore u=+30cm

Hope it helps you♥️♥️

Always rember the formula and the sign conventions!!

Answer 2

Given,

focal length, f = -15 cm

Distance of image, v = -10 cm

Distance of object, u =?

We know that,

1/v - 1/u = 1/f

So, 

1/-10 - 1/u = 1/-15

So, -1/10 + 1/15 = 1/u

(-3 + 2)/30 = 1/u

-1/30 = 1/u

Therefore u = -30 cm

Thus object is placed 30 cm away from the concave lens.

 

 Negative sign shows that object is at 30cm in front of the lens.
Hope this is helpful to you..
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