Question

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What is principal focus and focal length?​

Answer 1

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Principle focus is the point on the axis of a convex lens, where the parallel rays of light from one side of the lens. meet on other side after refraction. Distance between optical centre to principle focus point is the focal length

Answer 2

Answer:

The maximum value of E in an electromagnetic wave propagating in X-direction is 1000 Newton/coulomb which is in Z direction.