For correcting myopia, a concave lens is used. According to the convention for lens power, the power of such a corrective lens is which sign?

1. By convention, a concave (diverging) lens has negative focal length. 2. Power is $P = \dfrac{1}{f}$, so a negative $f$ gives a negative power. 3. Myopia is corrected with a concave lens, so its power is negative. 4. A positive power would correspond to a convex lens, which corrects hypermetropia instead. _Source: Samacheer Kalvi (TN SCERT) Class 10 Science, Unit 2 Optics "Power of a Lens", p.30_