Verified Solution • 2025–26 Session moderate

QJEEM12Ph8998: JEE Main 2012 Physics - Class 11 JEEM12Ph8998 Solution: A spectrometer gives the following reading when used to measure …

A spectrometer gives the following reading when used to measure the angle of a prism.
Main scale reading: 58.5 degree
Vernier scale reading : 09 divisions
Given that 1 division on main scale corresponds to 0.5 degree. Total divisions on the vernier scale is 30 and match with 29 divisions of the main scale. The angle of the prism from the above data

Multiple Choice Options

  • A 58.59 degree
  • B 58.77 degree
  • C 58.65 degree
  • D 59 degree

Step-by-Step Verified Solution

30 vernier scale divisions coincide with 29 main scale divisions.

Therefore 1 V.S.D = 2930{{29} \over {30}} M.S.D

Least count = 1 M.S.D - 1 V.S.D

= 1 M.S.D - 2930{{29} \over {30}} M.S.D

= 130{{1} \over {30}} M.S.D

= 130{{1} \over {30}} ×\times 0.5o

Reading of Vernier = Main Scale Reading + Vernier scale reading ×\times Least count

Given that,

Main Scale Reading = 58.5

Vernier scale reading = 09 division

∴\therefore Reading of Vernier = 58.5o + 9 ×\times 0.5∘30{{0.5^\circ } \over {30}}

= 58.65o

Related Learning Resources & Exam Preparation

JEE Main PYQ Question Bank
Browse year-wise authentic previous years' questions with solutions
Authentic CBT Mock Tests
Simulate official exam environment with live timer and percentile scoring