An object is placed at the following distances from a convex lens of focal length 10 cm:
a) 8 cm, b) 15 cm , c) 20 cm , d) 25 cm
Which position of the object will produce:
i) a diminished real image?
ii) a magnified real image?
iii) a magnified virtual image?
iv) an image of the same size as the object?

Explanation

The focal length of this convex lens is 10 cm. This means that f=10cm.
i) A diminished real image is formed by a convex lens when the object is beyond 20 cm ( or more than 20 cm) is 25 cm. Thus, 25 cm position of the object will produce a diminshed real image.
ii) A magnified real image is formed by a convex lens when the object is between f and 2f, that is between 10 cm and 20 cm. In this problem, the distance which is between 10 cm and 20 cm is 15 cm. So, 15 cm position of the object will produce a magnified real image.
iii) A magnified virtual image is formed by a convex lens when the object is within focus, at a distance less than the focal length f or less than 10 cm. In this problem, the distance which is less than the focal length of 10 cm is 8 cm. Thus, 8 cm position position of object will produce a magnified virtual image.
iv) An image of the same size as the object is formed by a conex lens when the object is at 2f or twice the focal length from lens. Here `2f=2 xx 10=20` cm. So, the 20 cm position of the object will produce an image of the same size as the object.
If the question is asked in the examination, then the answer can just be written as:
i) 25 cm, ii) 15 cm, iii)8cm, iv) 20cm