Two lenses A and B have focal lengths of + 20 cm and, -10 cm, respectively. (a) What is the nature of lens A and lens B ? (b) What is the power of lens A and lens B ? (c) What is the power of combination if lenses A and B are held close together ?
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a)- For converging lenses, the focal length is always positive, while diverging lenses always have negative focal lengths. so A is converging and B is diverging lens.