Question

a convex lens having power 4D and it form real and inverted image magnified by 3 times find object distance?​

Answer 1

Answer:

Given magnification m=−1 and object distance u=−20cm

We know magnification m=

u

−v

v=−mu=(−1)(−20)=20cm

Now from lens formula we have,

v

1

−

u

1

=

f

1

20

1

−

20

−1

=

f

1

f=10cm

Now powerp=

f

1

=

100

10

1

=10 D

Step-by-step explanation:

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Answer 2

$\huge\underbrace\red{ᴀɴsᴡᴇʀ}$

Power = 4 D

u = -10cm

f=?

v = ?

As we know,

$\sf \: P = \frac{100}{f} \\ \\ \sf \longrightarrow \: f = \frac{100}{4} \\ \\ \sf \longrightarrow \: f = 25$

Now,

$\sf \longrightarrow \: \frac{1}{f} = \frac{1}{v}- \frac{1}{u} \\ \\ \sf \longrightarrow \: \frac{1}{v} = \frac{1}{f}+ \frac{1}{u} \\ \\ \sf \longrightarrow \: \frac{1}{v} = \frac{1}{25} + \frac{1}{( - 10)} \\ \\ \sf \longrightarrow \: \frac{1}{v} = \frac{(2 - 5)}{50} \\ \\ \sf \longrightarrow \: v = \frac{( - 50)}{3} \\ \\ \sf \longrightarrow \red{v = - 16.66 \: cm}$

$\rule{300px}{.8ex}$