Question

Fill in the blanks for convex lens.

f (m)	0.2	…	0.1
P (D)	…	2	…
h1	…	5	10
h2	−30	−20	…
M	−2	…	−0.5

Answer 1

As the power of a lens in dioptre, it is given by the relation:

f (m)	0.2	0.5	0.1
P (D)	5	2	10

(i) f = 0.2m

(ii) P = 2D

(iii) f = 10 m

Also magnification (M) of a spherical lens gives the relative extent to which the image of an object is magnified with respect to the object size and that can be given as:

M = h₂/h₁

h1	15	5	10
h2	−30	−20	−5
M	−2	−4	−0.5

(i) h₂ = −30

M = −2

M = h₂/h₁

⇒ −2 = (-30)/h₁

⇒ h₁ = 15

(ii) h₂ = −20

⇒ h₁ = 5

⇒ M =?

M = h₂/h₁

⇒ M = (-20)/5

⇒ M = −4

(iii) h₁ = 10

M = −0.5

h₂ = ?

M = h₂/h₁

⇒ −0.5 = h₂/10

⇒ h₂ = −5