how do v decide the sign of image dis nd object dis in case of lens whenever we get d sign of the image +ve how do v decide dat its on RHS or LHS OF D LENS.In case of mirror when object is some dis in front of it then image will b formed same dis at d back of it.is it same for object behind d mirror.how do v decide real and virtual object nd image in case of mirror

Dear student,

Lens formula: The expression which shows the relation between u, v and f is called lens formula.

           1/f = 1/v – 1/u  

Lens maker formula: If R₁ and R₂ are the radii of curvature of first and second refracting surfaces of a thin lens of focal length f and refractive index  µ (w.r.t. surrounding medium) then the relation between f,  µ, R₁ and R₂ is known as lens maker formula.         

          1/f = (µ – 1) {1/R₁ – 1/R₂}

Magnification

The ratio of the size of the image to the size of object is called magnification.

(i)         Transverse magnification : m = 1/O = v/u = f/f+u = f–v/f (use sign convention while solving the problem)

(ii)        Longitudinal magnification : m = 1/O = v₂–v₁/u₂–u₁. For very small object

               m = dv/du = (v/u)² = (f/f+u)² = (f–v/f)²

(iii)       Areal magnification : m_s = A_i/A_o = m² = (f/f+u)²

            (A_i = Area of image, A_o = Area of object)

draw diagram.it will clear from that wht is sign of v. it will also clear frm dat diagram that the image is real or virtual.