Question

5. The focal point is located 20.0cm from a double concave lens. An object is placed 12cm fror
the lens. Determine the image distance.
1) d; = -6.5cm 2) di = -5.5cm 3) di = -4.5cm 4) di = -7.5cm ​

Answer 1

Answer:

Given: An object is placed at a distance of 20 cm from a convex mirror or radius of curvature 40 cm.

To find the distance at which the plane mirror should be placed such that the images due to the mirror and the plane mirror are in the same plane

Solution:

According to the given criteria,

Object distance from convex mirror, u=−20cm

Radius of curvature of convex mirror, R=40cm

Focal length of the convex mirror, f=

2

R

=

2

40

=20cm

Now applying the mirror formula we get,

f

1

=

v

1

+

u

1

⟹

20

1

=

v

1

+

−20

1

⟹

v

1

=

20

1

+

20

1

⟹v=10cm

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