1.

an object 3 cm high is placed 20cm from convex lens of focal lenght 12 cm. find the nature,position,magnification and height of the image.​

Answer»

An object 3 cm high is placed 20CM from convex lens of focal lenght 12 cm.

We have to find the nature, position, magnification and HEIGHT of the image.

From above data we have; height of object (h) is 3 cm, object distance (u) is -20 cm and focal length (f) is 12 cm.

USING lens formula:

1/f = 1/v - 1/u

Substitute the values in the above formula,

→ 1/12 = 1/v - 1/(-20)

→ 1/12 = 1/v + 1/20

→ 1/12 - 1/20 = 1/v

→ (5 - 3)/60 = 1/v

→ 1/30 = 1/v

→ 30 = v

Therefore, the image distance from the lens is 30 cm.

Using Magnification formula:

m = v/u

Substitute the values,

→ m = 30/(-20)

→ m = -1.5

Also, m = h'/h

→ -1.5 = h'/3

→ -4.5 = h'

So, the height of the image is 4.5 cm.

Nature of the image:

Image is real, INVERTED and larger than the object.


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