Question

Two slip gauges of 10 mm width measuring 1.000 mm and 1.002 mm are kept side by side in contact with each other lengthwise. An optical flat is kept resting on the slip gauges as shown in the figure. Mono-chromatic light of wavelength 0.0058928 mm used in the inspection. The total number of straight fringes that can be observed on both slip gauges is

• A. 6
• B. 8
• C. 2
• D. 13

Answer 1

The correct option is C 2

$\Delta h=\frac{N}{2}\times \frac{\lambda }{2}$

$\Delta h=\text{difference in the height of slip gauges.}$

$\Delta h=1.002-1.000=0.002mm$

$\lambda =\text{wavelength}$

$\text{Total number of straight fringes,}$

$N=\frac{4\times \Delta h}{\lambda }=\frac{4\times 0.002}{0.0058928}$

$=1.357\approx 2$