13. Consider two identical crystals A and B. The defect density ( # of point defect/potential defect site) in A and B are 104 and 103 respectively. What can be a possible reason for this difference? 14. What is the dislocation density of the two crystals shown next? Crystal size: 1m1m1m. 15. Which of these crystals shown is likely to have lower yield stress? Why? 16. Two similar edge dislocations on the same slip plane repel each other, opposite dislocations attract. Why? 17. Two polycrystalline metals, A and B, have average grain size of dA and dB respectively, dB>dA. 18. 'as higher yield strength? Why