13.3.4 | правка #18639 | Решения Савченко

Statement

13.3.4. At what distance from the lens is the object located, if the distance between the object and its actual image is minimal? The focal length of the lens is $$f$$ .

Solution

For a thin len,
$\frac{1}{s}+\frac{1}{s'} = \frac{1}{f}$
as the distance between the object and its actual image is minimal, $$s = s'$$ ,
$\frac{2}{s} = \frac{1}{f}$
$$s = 2f$$

Answer

$$s = 2f$$