Question

Indicate which one of the following statements is not correct?
(a) Intensities of reflections from different crystallographic planes are equal
(b) According to Bragg's law higher order of reflections have high $\theta$ values for a given wavelength of radiation
(c) For a given wavelength of radiation, there is a smallest distance between the crystallographic planes which can be determined
(d) Bragg's law may predict a reflection from a crystallographic plane to be present but it may be absent due to the crystal symmetry

• A.
• B.
• C.
• D.

Answer 1

Answer: (B)

Answer 2

Moseley studied the $X$-ray spectra of various elements. The spectral line observed were of
(i) short wavelength $-K$ series and
(ii) long wavelength $-L$ series. $K_{\alpha}$ line is most intense in the $K$-series. Moreover, he observed that the wavelength of the $K_{\alpha}$ line decreases with increase in the atomic number of the element as the target. If a graph is plotted between the square root of the frequency and the atomic number of the element emitting the line, it is a straight line Thus, $\sqrt{f} \propto Z$
Where $\sqrt{f}$ is the frequency of the radiation and $Z$ is the atomic number of the element.