A thin concave and a thin convex lens are in contact. The ratio of the magnitude of power of two lenses is \(\frac{2}{3}\) and the focal length of combination is 30 cm. The focal length of the convex
1
10 cm
2
12 cm
3
13 cm
4
20 cm
A thin concave and a thin convex lens are in contact. The ratio of the magnitude of power of two lenses is \(\frac{2}{3}\) and the focal length of combination is 30 cm. The focal length of the convex