A) generally, the crystals are expected to expand by temperature. what are the reasons for this? in which cases, it can be expected to decrease the size of the objects whose temperature increases.
b) explain the reasons for the formation of the forbidden band.
c) write down the reason why good conductors are used in mirror construction.
d) show sdia = sbas × sfcc for the structure factors; sdia, sbas, sfcc which are diamond crystal, the base of the diamond, and for fcc respectfully.

the part of the wave he is travelling on is the crest

causes

fossil fuels burn

cities become more industrialized

human population grows worldwide

russian is not my first language, so i'm afraid i can't write out an answer in russian, but hopefully you can find a way to do so. here's my best translation of the problem: you're given a plot of a particle's position in one-dimensional space over time, and you're asked to find either the total distance traveled by the particle after 6 seconds had elapsed, or the total displacement of the particle after 6 seconds.

if you want the total distance traveled, you would first need to determine the particle's velocity as a function of time, then integrate that over the 6-second interval. we know the position function is quadratic with roots at 0 and 6, so we have

where is unknown. because the position is parabolic, there is symmetry about the midpoint at , and we know that

so that the position function is

which means the velocity is

then the total distance traveled is

so the total distance traveled is 20 m.

on the other hand, if you want to find displacement: the particle starts at and ends at , so its displacement is 0.