An object is placed perpendicular to the principal axis of a convex lens of focal length 8 cm. The distance of the object from the lens is 12cm. Find the position and nature of the image.

OR


Define the term magnification as referred to spherical mirrors. If a concave mirror forms a real image 40 cm from the mirror, when the object is placed at a distance of 20 cm from its pole, find the focal length of the mirror.


Given: Lens is convex


Distance of the object from the lens (u) = -12cm


Focal length (f) = 8cm


Position of the image =?


To calculate position of the image, apply the lens formula:








• v = 24cm


Thus, the position of the image is 24cm.


A negative sign in the value of the magnification indicates that the image is real. A positive sign in the value of the magnification indicates that the image is virtual. Hence, to find the nature of the image, we will calculate magnification:




• m = -2


Thus, the nature of the image is real because magnification shows a negative value.


OR


Magnification: Magnification produced by a spherical mirror gives the relative extent to which the image of an object is magnified with respect to the object size.


It is usually represented by the letter (m). It is expressed as the ratio of the height of the image to the height of the object. The formula for magnification is given as:



Given: v = -40cm


u = -20cm


To calculate the focal length of the mirror, apply the formula:







Thus, the focal length of the mirror is -40/3.


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