A convex lens of focal length f1 and a concave lens of focal length f2 are placed in contact. The focal length of the combination isPhysics A. f2 + f1 B. f2 – f1 C. f1f2/f2+f1 D. f1f2/f1-f2
Two automobiles are 150 kilometers apart and traveling toward each other. One automobile is moving at 60km/h and the other is moving at 40km/h mph. In how many hours will they meet?
The most fundamental of all sciences which provides basic principles and fundamental laws to other branches of science is
