# List Four Characteristics of the Image Formed by a Concave Lens of Focal Length 20 Cm When the Object is Placed at a Distance of 40 Cm from Its Optical Centre. - Science

Numerical

List four characteristics of the image formed by a concave lens of focal length 20 cm when the object is placed at a distance of 40 cm from its optical centre.

#### Solution

Characteristics of the image formed by a concave lens :

According to sign convensions :

f = 20  "cm" ; u = -40  "cm"

we know that ,

-1/f = -1/"v" - 1/u

therefore 1/"v" = 1/f - 1/u = 1/20 - 1/40 = 20/800

therefore 1/"v" = 1/40

therefore "v" = 40   "cm"

(i) image will be formed at 40 cm from the optical centre.

(ii) Radius of curvature of lens :

R = -2f  ∴ R = -2 xx 20 = -40  "cm"

(iii) Since image distance is positive, therefore image is virtual.

(iv) Image will be erect.

(v) Image will form opposite side of the lens.

Is there an error in this question or solution?