A pearlitic steel is observed under an optical microscope which has a numerical aperture (N.A) of 1.5 and uses the radiation of 4500A. The minimum lamellar spacing (in A) which can be resolved using this microscope is

A. increasing the size of the sample B. smooth polishing of the surface of the sample C. having compressive residual stresses at the surface D. having tensile residual stresses at the surface

A. Providing a contrasting background for visible dye indications B. Making the penetrant water washable C. Penetrating into discontinuities open to the surface D. Dissolve organic soils on the test piece surface

A. Increases, increases B. Increases, decreases C. Decreases, increases D. Decreases, decreases

A. Square based diamond pyramid with 136° included angle B. Conical shape steel with 120° apex angle C. Conical shaped diamond with 120° apex angle D. 10 mm diameter hardened steel ball