Question

A concavee lense of power -2. OD is used to form an
image of an object of size 9cm kept at a
distance of 25 cm from it. Find the nature, size
and position of the
image
formed​

Answer 1

it is just an example:-

Answer:

What is the power of concave lens of focal length 25cm?

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Parveen Kumar

4 weeks ago

Since,

it is concave lens so the focal length of a concave lens is considered negative

Then,

Focal length (f) = - 25 cm

= - 25 /100 m

= - 0.25 m

Now,

P= 1/f (in metre)

P = -100/25 m

P = -4 D

Now, the power of concave lens is -4 Dippers.

Answer 2

Given :

Power of concave lens = -2 D

Size of object = 9 cm

Distance of object = 25 cm

To Find :

Nature, size and position of the image.

Solution :

First of all we have to find focal length of lens.

➙ f = 1 / P

➙ f = 1 / (-2)

➙ f = -0.5 m

➙ f = -50 cm

❖ Distance of image can be calculated by using lens formula$.$

➙ 1/v - 1/u = 1/f

➙ 1/v - 1/(-25) = 1/(-50)

➙ 1/v + 1/25 = -1/50

➙ 1/v = -1/50 - 1/25

➙ 1/v = (-1 - 2) / 50

➙ v = -50/3

➙ v = -16.67 cm

❖ Size of the image :

➠ m = v/u = h'/h

• h' denotes size of image
• h denotes size of object

➠ (-16.67)/(-25) = h'/9

➠ h' = 9 × 0.67

➠ h' = 6.03 cm

❖ Nature of the image :

• Virtual
• Erect
• Small