An object is placed at a distance of 20cm from the optical centre of a convex lens of focal length 15cm .find the distance of the image from the lens what will be the height of the image if the object is 4cm tall

       Use the lens form:

                                1/f=1/v-1/u

                                1/30=1/v-(1/-20)

                                 1/30=1/v+1/20

                                 1/30-1/20=1/v

                                  2-3/60=1/v

                                  -1/60=1/v                    ;;;v =  -60 cm

              m = h of image/h of object  =  v/u

                                    H/2 = -60/-20

                                     H = 3*2

                                       H = 6 cm

i don't understand is there any other way you can rephrase it plz let me know in the comments and i will do it.

explanation:

that would be because of both gravity and friction. so     c