If an object is kept at a distance of 50 cm from a convex lens of focal length 20 cm. then the image distance is:

Correct option is A

The correct answer is (a) 33.3 cm​

Explanation:

Step 1: Determine if the focal length is positive or negative. The lens is converging so the focal length is positive.

Step 2: Determine if the object distance is positive or negative. The object is real so the object distance is positive.

Step 3: Use the equation d_i= 1/ (1/f-1/d₀)

The distance of the image from the lens is d_i= -33.3 cm

The image is virtual and will be on the same side of the lens as the object.

where, f=is the focal length, d₀= the distance of the object from the lens, and d_i=the distance of the image from the lens