Question

an object is placed at a distance 50 cm from a convex lense of focal length 60 cm.find the image distance and magnification ​

Answer 1

Explanation:

u=−60cm

u

−v

=

2

1

⇒

−60

−v

=

2

1

⇒v=30cm

⇒

v

1

+

u

1

=

f

1

⇒

f

1

=

30

1

+

−60

1

⇒

f

1

=

60

2−1

=

60

1

⇒f=60cm

Now magnification=

3

1

u

−v

=

3

1

⇒v=

3

−u

∴

v

1

+

u

1

=

f

1

⇒

3

−u

1

+

u

1

=

f

1

⇒

u

−3

+

u

1

=

60

1

⇒

u

−2

=

60

1

⇒u=−120cm

Answer 2

f=60 cm,u=-50 cm ,v=?
By lens formula we have,
(1/f)=(1/v)-(1/u)
1/60=1/v-(1/-50)
1/60=(1/v)+(1/50)
1/v=(1/60)-(1/50)
1/v=(5-6)/300
1/v=-1/300
v=-300 cm
So the image distance is 300 cm away
Magnification(m)=v/u
=-300/-50
=6