An object 5 cm high is held 25 cm away from a converging lens of focal length 10 cm. Draw the ray diagrams and find the position, size and the nature of the image formed.
Object distance u = -25 cm
Image distance v = ?
Focal length f = 10 cm
Using the lens formula
=
∴ v = 16.67 cm
Positive sign shows that the image formed is to the right of the lens and is at 16.67 cm from the lens, i.e., the image is formed between F and 2f. Since only the real and inverted image is formed on the right hand side of a convex lens, therefore, the image formed is real and inverted.
Magnification, m =
= -0.67.
Image formed is two times magnified and is inverted.
Again m =
where h1 and h2 are the sizes of objects and imagesi.e., -0.67 = 
(h1 is always positive)
h2 = - 3.35 cm
Size of image is 3.35 cms, hence smaller than the object and is always inverted.
Image distance v = ?
Focal length f = 10 cm
Using the lens formula
=
∴ v = 16.67 cm
Positive sign shows that the image formed is to the right of the lens and is at 16.67 cm from the lens, i.e., the image is formed between F and 2f. Since only the real and inverted image is formed on the right hand side of a convex lens, therefore, the image formed is real and inverted.Magnification, m =
= -0.67.Image formed is two times magnified and is inverted.
Again m =
where h1 and h2 are the sizes of objects and imagesi.e., -0.67 = (h1 is always positive)h2 = - 3.35 cm
Size of image is 3.35 cms, hence smaller than the object and is always inverted.
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