The thickness at the centre of a plano convex lens is 3 mm and the diameter is 6 cm. If the speed of light in the material of the lens is 2 × 108 ms-1. The focal length of the lens is ________.
1
30 cm
2
15 cm
3
1.5 cm
4
0.30 cm
The thickness at the centre of a plano convex lens is 3 mm and the diameter is 6 cm. If the speed of light in the material of the lens is 2 × 108 ms-1. The focal length of the lens is ________.