The skid in a stylus type roughness measuring instrument is used to provide ............ A .............. and define ................... B .............. geometrical profile of the surface.

$$A.$$ support / datum
$$B.$$ micro / macro

The fit on a hole-shaft pair system is specified as $$H7$$-$$s6$$. The type of fit is

The most widely used reinforcement in modern day $$FRP$$ tennis racket is

In an interference microscope, a groove produces a band distortion of $$4$$ band spacing. If the wave length of the monochromatic light source is $$0.5microns,$$ the groove depth is ......................$$mm$$