A thin glass (refractive index 1.5) lens has optical power of-5D in air. Its optical power in a liquid medium with refractive index 1.6 will be A) 25D
B) -25D
C) 1D
D) 5D/8​

I'm thinking it's 2 you are asked to explain the earth's magnetic field. which is the best reply? 1. the earth's magnetic south is similar to the north pole of a magnet. 2. the earth's core has a strong magnetic charge similar to the south pole of a magnet. 3. the earth's geomagnetic south is similar to the south pole of a magnet. 4. the earth's magnetic charge is not centered at either pole; it varies based on location.