NON DESTRUCTIVE TEST

$7.$If an array which has a limit of focus of $50$ mm is changed from $2\mathrm{.}5$ MHz to $5$ MHz$,$ what is the new limit of focus?

a$\mathrm{.}200$ mm

b$\mathrm{.}150$ mm

c$\mathrm{.}100$ mm

d$\mathrm{.}75$ mm

$8.$What value of K should be used to calculate the $-20$dB isobar?

a$\mathrm{.}1\mathrm{.}08$

b$\mathrm{.}0\mathrm{.}56$

c$\mathrm{.}1\mathrm{.}22$

d$\mathrm{.}1\mathrm{.}48$