(i) Define the angular magnification of a magnifying glass.

(ii) Derive an equation for the angular magnification of a magnifying glass with the image at infinity.

An object is positioned 8.00 cm from a magnifying glass of focal length 15.0 cm.

(i) Calculate the position of the image.

(ii) Calculate the linear magnification.

(iii) The image is upright and magnified. State a further property of the image.

(i) ratio of angle subtended by image at eye to angle subtended by object at the near point;

(ii) ${\theta _o} = \frac{{{h_o}}}{{25}}$;
${\theta _i} = \frac{{{h_o}}}{f}$;
$M = \frac{{{\theta _i}}}{{{\theta _o}}} = \frac{{{h_o}}}{f} \times \frac{{25}}{{{h_o}}} = \frac{{25}}{f}$;
Award [3] for use of symbol (e.g. D) to represent distance to near point (25 cm).

or

realizes object is at f;
obtains at least 1 correct angle as either $\frac{h}{{25}}$ or $\frac{h}{{D}}$ or $\frac{h}{{f}}$;

shows that $M = \frac{D}{f}$ or $M = \frac{25}{f}$;

(i) $\left( {\frac{1}{f} = \frac{1}{v} + \frac{1}{u}} \right)$
$\frac{1}{{15}} = \frac{1}{v} + \frac{1}{8}$;
$v = \left(  -  \right)17.1{\rm{cm}}$;

(ii) 2.14 or –2.14;

(iii) virtual;