91影视

(a)

The angle of constructive interference${\text{胃}}_{\text{min}}=\text{35}掳$.

When there is constructive interference, Bragg's equation can be used to describe the relationship between the quantities.

$\mathbf{\text{2d蝉颈苍胃=尘位鈥︹�︹�︹�︹�︹��(1)}}$

Using equation$\text{(1)}$.

$\begin{array}{l}\text{2d蝉颈苍胃=尘位}\\ \text{2蝉颈苍胃=}\frac{\text{尘位}}{\text{d}}\\ \frac{\text{位}}{\text{d}}\text{=}\frac{\text{2蝉颈苍胃}}{\text{m}}\end{array}$

${\text{胃}}_{\text{min}}$is the minimum angle for the constructive interference, so$\text{m=1}$.

$\begin{array}{c}\frac{\text{位}}{\text{d}}\text{=}\frac{\text{2}脳\text{蝉颈苍胃}}{\text{m}}\\ \text{=}\frac{\text{2}脳\text{sin}(\text{35}掳)}{\text{1}}\\ \text{=1.15}\end{array}$

Therefore the ratio of$\frac{\text{位}}{\text{d}}$ is $\text{1.15}$in the spacing between the atomic planes.

From Equation$\text{(1)}$the minimum value for$\text{蝉颈苍胃}$is$\text{1}$.

So,

$\begin{array}{l}\text{2d蝉颈苍胃=尘位}\\ \text{蝉颈苍胃=}\frac{\text{尘位}}{\text{2d}}\\ \text{1}鈮�\frac{\text{尘位}}{\text{2d}}\\ \text{m}鈮�\frac{\text{2}}{\frac{\text{位}}{\text{d}}}\end{array}$

Insert$\frac{\text{位}}{\text{d}}\text{=1.15}$

$\begin{array}{c}\text{m}鈮�\frac{\text{2}}{\frac{\text{位}}{\text{d}}}\\ 鈮�\frac{\text{2}}{\text{1.15}}\\ \text{=1.74}\end{array}$

Here m can notbe considered as $\text{2}$.So this is an invalid value of the.$\text{蝉颈苍胃}$

As a result, the only integer that exists is$\text{m=1}$ .

This is the smallest angle at which constructive interference was detected. As a result, constructive interference is not visible from any other angles.