Practice problem 5

Here there are two possible solutions. Two convergeing lenses can be used with a focal point between them. Or, a converging lens and a diverging lens with a focal point of the converging lens beyond the diverging lens.

Practice problem 8

(d) The relative intensity here must be discussed in terms of the N dependence of the intensity of the principal maximum peak. (See the later part of this video.)

Review problem 9

Here, we can use $2 d \sin \phi = m \lambda$. $d$ is the spacing between lattice planes, and so is not equal to $a_0$. $\phi$ is not equal to $\theta$. (See this video).)

Review problem 10

(b) This part can be considered a bit out of the scope, since the change of $f$ due to the change in Snell's law is actually quite complicated. Additionally, we also must consider the fact that when the ray goes through the center, it no longer goes through it as a straight line. This is also due to Snell's law, and this change is simple to figure out in small angle approximation. The combined effect of these two causes or the effect of the second cause alone (assuming that the object does not move) can be discussed. The answer is a bit ambiguous if the combined effect is considered.