Which lens has positive and which lens has negative power?

Which surface has a positive and which surface has a negative power?

Under what conditions will a convex lens have a negative and a concave lens a positive power?

A thin glass (refractie index = 1.5) lens has optical power of -5 D in air.Its optical power in a liquuid of refractive index 1.6 will be

Which has the highest oxidizing power?

Which of the following has negative temperature coefficient of resistance?

Which of the following has a negative temperature coefficient?