Question

With the help of ray diagram explain the nature, size and position of the image formed by a convex lens. when object is placed at

(i) infinity

(ii) beyond C

(iii) placed at C 

(iv) Placed between F and C,

(v) placed at F

(vi) placed between F and optical centre O.

Answer 1

(i) Object at infinity: When an object is placed at infinity, a real image is formed at the principal focus. The size of the image is much smaller than that of the object.

Object at infinity

(ii) Object placed beyond C (>2F): When an object is placed behind the center of curvature(beyond C), a real and inverted image is formed between the center of curvature and the principal focus. Th e size of the image is the same as that of the object.

Object placed beyond C(>2F)

(iii) Object placed at C: When an object is placed at the center of curvature, a real and inverted image is formed at the other center of curvature. The size of the image is the same as that of the object.

Object placed at C

(iv) Object placed between F and C: When an object is placed in between the center of curvature and principal focus, a real and inverted image is formed behind the center of curvature. The size of the image is bigger than that of the object.

Object placed between F and C

(v) Object placed at the principal focus F: When an object is placed at the focus, a real image is formed at infinity. The size of the image is much larger than that of the object.

Object placed at the principal focus F

(vi) Object placed between the principal focus F and optical centre O: When an object is placed in between principal focus and optical centre, a virtual image is formed. The size of the image is larger than that of the object.

Object placed between the principal focus F and optical centre O