Question
Two thin lenses of focal lengths $f_1 = +20 \text{ cm}$ and $f_2 = -10 \text{ cm}$ are in contact. The power of the combination is:
Options
- A
$-5 \text{ D}$
- B
$+5 \text{ D}$
- C
$-3 \text{ D}$
- D
$+3 \text{ D}$
Two thin lenses of focal lengths $f_1 = +20 \text{ cm}$ and $f_2 = -10 \text{ cm}$ are in contact. The power of the combination is:
$-5 \text{ D}$
$+5 \text{ D}$
$-3 \text{ D}$
$+3 \text{ D}$