JEE MAIN - Physics (2022 - 26th June Evening Shift - No. 25)
A travelling microscope is used to determine the refractive index of a glass slab. If 40 divisions are there in 1 cm on main scale and 50 Vernier scale divisions are equal to 49 main scale divisions, then least count of the travelling microscope is __________ $$\times$$ 10$$-$$6 m.
Answer
5
Explanation
40 M = 1 cm
$$\Rightarrow$$ M = 0.025 cm .......... (1)
Also, 50 V = 49 M
$$\Rightarrow$$ Least count = M $$-$$ V = M $$-$$ $${{49} \over {50}}$$ M = $${{M} \over {50}}$$
$$\Rightarrow$$ LC = $${{0.025} \over {50}}$$ cm
= $${{250} \over {50}}$$ $$\times$$ 10$$-$$6 m
$$\Rightarrow$$ LC = 5 $$\times$$ 10$$-$$6 m
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