Question

an object 4vm in size is placed in front of a concave mirror of radius of curvature of 30cm.find the position of the image and the nature of the image formed
​

Answer 1

Answer:

Given, h

o

=4cm,u=+30cm,f=+20cm

To find: v,h

i

and nature of image

From mirror formula, we have

u

1

+

v

1

=

f

1

∴

v

1

=

f

1

−

u

1

=

uf

u−f

v=

uf

u−f

=

30cm−(20cm)

30cm×20cm

=

+10

600cm

=+60cm

Magnification, m=

h

o

h

i

=−

u

v

or h

i

=−

u

v

×h

o

=−(−

+30fm

+60cm

)×4cm=−8cm

Thus, image is formed at a distance of 60cm in front of the mirror. Height of the image is 8cm. As v is positive, the image is real. Since h

i

is negative, it is inverted.

Answer 2

Answer:

object distance=-4cm

Focal length=radius/2

f=15cm

By using mirror formula

1/v+1/u=1/f

1/v=1/f+1/u

1/v=1/15+1/(-4)

1/v=1/15-1/4

1/v=-60/11

Nature of image is virtual and erect