Question $5$

$($a$)$ Explain the difference between defects and discontinuities.

$(2$ marks$)$

$($b$)$ List the common NDT methods used to detect defects or discontinuities on a surface weld.

$(4$ marks$)$

$($c$)$ List the common NDT methods for detecting internal weld defects or discontinuities.

Sketch the working principle of one of the listed methods.