Question

h is 2cm f is 10cm u is -15cm
find v and h dash of a convex lens ​

Answer 1

Magnification of image is, ∣m∣=2 as image size (h

′

) is double the object size (h)

Thus, m=±2

as for a less, m=

u

v

(object distance =u , image distance =v)

⇒

u

v

=±2 ⇒v=2u or v=−2u

(i) case I : v=2u⇒u=v/2 then by lens formula,

v

1

−

u

1

=

f

1

⇒

v

1

−

v

2

=

20

1

⇒v=−20 cm

(ii) case II : when v=−2u⇒u=−v/2, so

v

1

−

u

1

=

f

1

⇒

v

1

+

v

2

=

20

1

⇒v=20/3 cm

∴ Image distance can be 20 cm (if image is virtual) on can be 20/3 cm (if image is real)

for more understanding

go through ⬆️⬆️⬆️

Answer 2

Explanation:

Lens formula

1/f = 1/v - 1/u

1/10 = 1/v - (-15)

1/10 - 1/15 = 1/v

1/30 = 1/v

So, V= 30cm

h dash/h = v/u

h dash/2 = 30/-15

h dash = -4

So height of image is 4cm Real and inverted.