(a) The incident light rays must be parallel and close to the principal axis (b) Spherical aberration as a defect of curved mirrors: When a wide parallel beam is incident on a spherical mirror, it is not brought to the same focus. This makes the image distorted. (c) SEE THE DIAGRAM ABOVE (d) Accommodation is the ability of the eyes to alter its focal length to form a clear image (e) Quantitatively, (i) far point = infinity, Near point = 25 cm P\(_{near point}\) = \(\frac{1}{f}\) = \(\frac{1}{u}\) + \(\frac{1}{v}\) (ii) for near point, u = 0.25 m P\(_{near point}\) = \(\frac{1}{f}\) = \(\frac{1}{0.25}\) + \(\frac{1}{v}\) similarly, for far point, u = infinity(\infty) P\(_{far point}\) = \(\frac{1}{f}\) = \(\frac{1}{u}\) + \(\frac{1}{v}\) P\(_{far point}\) = \(\frac{1}{\infty}\) + \(\frac{1}{v}\) = 0 + \(\frac{1}{v}\) So, change in optical power \DeltaP = P\(_{near point}\) - P\(_{far point}\) \DeltaP = 4 + \(\frac{1}{v}\) - \(\frac{1}{v}\) \DeltaP = 4 dioptres.