Which of the following is not true for ?measurement of surface roughness a. Ra is surface parameter b. using dial indicator, we can calculate Ra c. Direction of measurement is perpendicular to the lay d. Rz is surface parameter Which of the following is not true for ?measurement of surface roughness a. Ra is surface parameter b. using dial indicator, we can calculate Ra c. Direction of measurement is perpendicular to the lay d. Rz is surface parameter