x1=-4 cm (distanta obiect-lentila)
f=6 cm
x2=?
[tex] \frac{1}{x2} - \frac{1}{x1} = \frac{1}{f} [/tex]
[tex] \frac{1}{x2} + \frac{1}{4} = \frac{1}{6} [/tex]
[tex] \frac{4 + x2}{4 \times x2} = \frac{1}{6} [/tex]
[tex]6(4 + x2) = 4 \times x2[/tex]
[tex]24 + 6x2 = 4 \times x2[/tex]
[tex]24 + 2x2 = 0[/tex]
[tex]24 = - 2x2[/tex]
[tex]x2 = - 12[/tex]
beta (marirea liniara)= x2/x1
beta= -12/-4= 3 => imagine virtuala
