Question

o lentila convergenta are distanta focala egala cu 20 de cm
calculati convergenta lentilei
determinati pozitia imaginii prin lentila pentru un obiect aflat la 10 cm distanta de lentila

Answer 1

Fie C = convergenta, f = distanta focala

$C = \frac{1}{f} = \frac{1}{0,2m} = 5\delta \text{ (5 dioptrii)}$

Fie x1 = distanta obiect-lentila = -0,1m , x2 = distanta imagine-lentila
Din legea lentilelor:

$\frac{1}{x_2} - \frac{1}{x_1} = \frac{1}{f}$
$\frac{1}{x_2} + \frac{1}{0,1m} = \frac{1}{0,2m}$
$\frac{1}{x_2} = \frac{1}{0,2m} - \frac{1}{0,1m}$
$\frac{1}{x_2} = \frac{-1}{0,2m}$
$-x_2 = 0,2m \implies x_2 = x_2 = -0,2m = -20cm$

Answer 2

[tex]Se~da:\\ \\ F=20cm=0,2m\\ \\ d=10cm=0,1m\\ \\ C=?dioptrii\\ \\ f=?m\\ \\ \\ Formule:\\ \\ C=\frac 1F\\ \\ \\ C=\frac 1f+\frac1d\\ \\ \frac 1f=C-\frac1d\\ \\ \frac 1f=\frac {C\times d -1}{d}\\ \\ f=\frac d{C\times d-1}\\ \\ \\ Calcule:\\ \\ C=\frac 1{0,2}=5dioptrii\\ \\ f=\frac {0,1}{5 \times 0,1-1}=-0,2m[/tex]