Explain why grain boundaries can act as barriers to dislo cation motion 29. state the difference between grain boundaries effect and grain size effect on strength of metals 30. the grain refinement effect on the strength can be described through the hall-petch equation explain and show why this equation is not valid in the nona-sized grains (< 50 nm)

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.

Question 1 (5 pts): what is the maximum distance for which you can you resolve the two individual headlights of an on-coming truck as two separate lights rather than one if the headlights are separated by 2.00 m and your eye has a diameter of 1.00 centimeter? assume a wavelength of 500 nm.

Which component of the earth’s atmosphere is decreased due to photosynthesis?