Question

When an object is placed in front of a convex lens of focal length 6cm, a real image, five times bigger than the object forms. Calculate the object distance.

Answer 1

Answer:

Focal length of the convex lens f=30cm

A convex lens forms a magnified real image when the image is inverted i.e. magnification must be negative.

Magnification of the lens m=−5

Using lens formula

v

1

−

u

1

=

f

1

We get

f

v

=1−m

∴

30

v

=1−(−5)

⟹ v=180cm

Using m=

u

v

(for lens)

∴ −5=

u

180

⟹ u=−36cm

Thus the object distance must be 36cm in front of the lens.

Answer 2

Answer:

Here is your required answer