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GATE 2026 ME – Question 33

Metrology and Inspection · Interferometry, form and finish measurement · 1 mark · Multiple choice

A two-dimensional surface profile is obtained over a sampling length by using a contact type stylus profilometer as shown in the figure below. A line AA parallel to the general lay of the trace is considered. The true heights from AA to the peaks and valleys (in $\mu$m) in the trace are also shown in the figure (not to scale).

The ten-point height average in $\mu$m is

A surface profile above the line AA. The peaks are 5.35, 6.7, 5.28, 4.32, 8.3, 6.3, 4.96, 6.9, 6.2 and 5.54. The valleys are 2.81, 1.92, 3.71, 2.82, 4.2, 1.97, 2.01, 2.9, 4.26 and 4.3.
  1. 4.57
  2. 5.99
  3. 3.09
  4. 2.90

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Show answer and explanation

Correct answer: (A) 4.57

Explanation

The ten-point height is the difference between the average of the five highest peaks and the average of the five lowest valleys. The five highest peaks are 8.3, 6.9, 6.7, 6.3 and 6.2, which add up to 34.4. The five lowest valleys are 1.92, 1.97, 2.01, 2.81 and 2.82, which add up to 11.53. So the value is $\frac{34.4 - 11.53}{5} = 4.57\ \mu$m.