Question

A 2.0 cm tall object is placed in front of convex lens. The distance of the object measured from optical centre is 15 cm. The focal length of the lens is 10 cm. Find the nature, position and size of the image. Also the magnification​

Answer 1

According to new cartesian sign convention,

Object distance, u=−15 cm

Focal length of the concave mirror, f=−10 cm

Height of the object, h

0

=2 cm

According to mirror formula,

v

1

+

u

1

=

f

1

⇒

v

1

=

f

1

−

u

1

=

−10

1

−

1−5

1

=

−10

1

+

15

1

or v=−30 cm

The image is formed at a distance of 30 cm from the mirror on the same side of the object.

It is a real image.

Magnification of the mirror, m=

u

−v

=

h

0

h

1

⇒

−15

−(−30)

=

2

h

1

⇒h

I

=−4 cm.

Negative sign shows that image is inverted.The image is real, inverted, of size 4 cm at a distance of 30 cm in front of the mirror.