Experimental Physics

JEE Main level, numerical answer, medium

34 of 70

Question 34 of 70

A travelling microscope is used to determine the refractive index of a glass slab. If 40 divisions are there in 1cm1cm on main scale and 5050 Vernier scale divisions are equal to 4949 main scale divisions, then least count of the travelling microscope is _____ ×10−6m\times {10}^{-6}m.

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Answer: 5

Given here, main scale reading, MS=140cmMS=\dfrac{1}{40}cm
And, 50×VS=49×MS50\times VS=49\times MS
Least count of travelling microscope is LC=MS−VSLC=MS-VS
=MS−4950MS=MS-\dfrac{49}{50}MS
=150×MS=\dfrac{1}{50}\times MS
=150×140cm=12000×10−2m=\dfrac{1}{50}\times \dfrac{1}{40}cm=\dfrac{1}{2000}\times {10}^{-2}m
=5×10−6m=5\times {10}^{-6}m

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