A myopic person has a far point of 1 m. The focal length of the corrective concave lens is:

1. The corrective lens must form the image of infinity at the far point (1 m in front). 2. For lens formula with u = ∞, v = -100 cm, we get f = -100 cm. 3. Hence a concave lens of focal length -100 cm (power -1 D) is needed. _Source: syllabus Science, Ch 10 "The Human Eye and the Colourful World", §10.2_