Question

an object of hight 5cm is placed near infront of a convex lens of focal length 20cm .and image of hight 20cm is formed behind the mirror find ? 1)u 2)v 3) distance between image and object​

Answer 1

Answer:

Given, u=-20cm

f=10cm

v=?

We know

f

1

=

v

1

−

u

1

10

1

=

v

1

−

20

(−1)

v

1

=

20

2−1

v=20cm

We know

magnification (M)=

h

o

h

i

=

u

−v

or,

−20

20

=−1=

h

o

h

i

since,h

0

=5cm

so,h

i

=−5cm

nature = real image

Answer 2

"" ❤️ Answer ❤️ ""

Formula:

v

1

+

u

1

=

f

1

Given,

v

1

+

(−20)

1

=

15

1

v

1

=

60

7

⇒ v=

7

60

v= 8.57≈ 8.6cm

The image is formed behind the mirror at a distance of

8.6 cm

m=

h

1

h

2

= −

u

v

→

5

h

2

=

−

20

8.57

∴

h

2

2.175 cm

Thus the image is 2.175 cm high, virtual and erect.

Hence, this is the answer.