Question

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Q33. An object of height 5 cm is held 30 cm away from a converging lens of focal length
10 cm. Find the position, size and nature of the image formed. 3​

Answer 1

Answer:

Given :

In convex lens,

Object height = 5cm.

Object distance = - 30cm

Focal length = 10cm.

To find:

The position, size and nature of the image formed.

solution:

Using lens formula,

The formula which gives the relationship between image distance, object distance and focal length of a lens is known as the lens formula.

The lens formula can be written as :

1 _ 1 = 1

v u f

where,

• v denotes image distance
• u denotes object distance
• f denotes focal length

by substituting all the given values in the formula,

1 _ 1 = 1

v u f

1 _ 1 = 1

v (---30) 10

1 + 1 = 1

v 30 10

1 = 1 _ 10

v 10 30

1 = 3 -- 1

v 30

1 = 1

v 15

v = 15 cm

thus, the position of image is 15cm.

Now, to find size of image we have to use magnification formula that is

m = h' = v

h u

where,

• m denotes magnification
• h' denotes image height
• h denotes object height

by substituting all the given values in the formula

h = v

h u

h' = 15

5 --30

h ' = _ 15 ×15

30

h' = _ 75

30

h' = 2.5cm

thus, the size of image is 2.5cm

Nature of image

• The image is real and inverted.
• The image is diminished.

I hope it may help you