A lens has a focal length of +20 cm. What type of lens is it?
Correct Answer: Convex lens
- Step 1: Understand what focal length means. Focal length is the distance from the lens to the point where light rays converge or diverge.
- Step 2: Identify the sign of the focal length. A positive focal length means the lens converges light.
- Step 3: Know the types of lenses. There are two main types: convex (converging) and concave (diverging).
- Step 4: Conclude that since the focal length is positive (+20 cm), the lens is a convex lens.
- Focal Length – The distance from the lens to the focal point, which determines the lens type.
- Lens Types – Convex lenses have positive focal lengths and converge light, while concave lenses have negative focal lengths and diverge light.
