Given:
50VSD=49MSD⇒1VSD=5049MSD
So least count will be
=1MSD−1VSD=201cm−5049⋅201cm
=501×201cm=0.01mm
As we know, μ=h′h=5.005.25
Applying log on both sides, we get
lnμ=lnh–lnh’
Differentiating both sides, we get
μdμ=hdh−h′dh′
For calculation, all errors will be added, therefore
dμ=[5.250.01+5.000.01]μ
=1041×10−3
Hence, x=41
In an experiment of measuring the refractive index of a glass slab using travelling microscope in physics lab, a student measures real thickness of…
JEE Main 2023 — Physics Mechanics
2023integerhard
In an experiment of measuring the refractive index of a glass slab using travelling microscope in physics lab, a student measures real thickness of the glass slab as 5.25mm and apparent thickness of the glass slab at 5.00mm. Travelling microscope has 20 divisions in one cm on main scale and 50 divisions on Vernier scale is equal to 49 divisions on main scale. The estimated uncertainty in the measurement of refractive index of the slab is 10x×10−3, where x is ______
Official previous-year question
Held on 29 Jan 2023 · Verified 1 Jul 2026.
Options
- A
- B
Did you get this right?
Sign in to track your attempts and accuracy.
Your note
Sign in to keep a private note on this question. Nothing you write is ever public.
JEE Main Mechanics in other years
More JEE Main Mechanics questions
If $\epsilon, E$ and $t$ represent the free space permittivity, electric field and time respectively, then the unit of $\frac{\epsilon E}{t}$ will be :
2026easy
When a part of a straight capillary tube is placed vertically in a liquid, the liquid raises upto certain height $h$. If the inner radius of the capillary tube, density of the liquid and surface tension of the liquid decrease by $1 \%$ each, then the height of the liquid in the tube will change by $\%$.
2026medium
The velocity of a particle is given as $\vec{v} = -x\hat{i} + 2y\hat{j} - z\hat{k}$ m/s. The magnitude of acceleration at point $(1, 2, 4)$ is _______ m/s$^2$.
2026hard
Suppose there is a uniform circular disc of mass $M \mathrm{~kg}$ and radius $r \mathrm{~m}$ shown in figure. The shaded regions are cut out from the disc. The moment of inertia of the remainder about the axis $A$ of the disc is given by $\frac{x}{256} M r^{2}$. The value of $x$ is $\_\_\_\_$. 
2026hard
A soap bubble of surface tension $0.04 \mathrm{~N} / \mathrm{m}$ is blown to a diameter of 7 cm. If $(15000-x) \mu \mathrm{J}$ of work is done in blowing it further to make its diameter 14 cm, then the value of $x$ is $\_\_\_\_$. ($\pi=22 / 7$)
2026medium
Other Physics topics for JEE Main
Keep practicing Mechanics
Work through every JEE Main Mechanics PYQ, year by year.