For a concave lens of focal length f , the relation between object and image distance u and v , respectively, from its pole can best be represented by ( u = v is the reference line):

Step-by-step solution

From the lens formula, 1 v - 1 u = 1 f ⇒ v = f - f 2 u + f now, if we plot a graph between u and v When u → ∞ ; v = f - f 2 ∞ = f and for u → 0 ; v = 0 Given that u = v is a reference line, therefore, d v d u = 0 + f 2 u + f 2 d v d u u = 0 = 0 + f 2 0 + f 2 = 1 The equation of tangent of the curve at the origin, v - 0 = 1 u - 0 ⇒ v = u