<span>c) convection currents in the mantle </span>
Option B The thickness of the central portion of a thin conveying lens can be determined very accurately by using a micrometer screw gauge.
<h3>What can be measured using a micrometer screw gauge?</h3>
One micrometer of thickness can be measured with a micron micrometre screw gauge. A Use of Micrometer Screw Gauge as like example Upon turning the screw of the micrometer screw gauge four times, a 2 mm space is covered.
<h3>What purposes does a micrometer serve?</h3>
A tool known as a micrometer is used to measure solid objects’ lengths, thicknesses, and other dimensions precisely and linearly.
<h3>What is the micrometer screw gauge’s SI unit?</h3>
The SI symbol m is also known as a micron, which is an SI-derived unit of length equaling 1106 meters, where 106 is the SI standard prefix for the prefix “micro-.” A micrometer is one-millionth of a meter.
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Answer:![r_2=11.81 cm](https://tex.z-dn.net/?f=r_2%3D11.81%20cm)
Explanation:
Given
![m_1=2.2\times 10^{-8} kg](https://tex.z-dn.net/?f=m_1%3D2.2%5Ctimes%2010%5E%7B-8%7D%20kg)
![m_2=4.8\times 10^{-8} kg](https://tex.z-dn.net/?f=m_2%3D4.8%5Ctimes%2010%5E%7B-8%7D%20kg)
same charge on both masses
potential Energy due to Magnetic Field =Kinetic Energy of Particle
![qV=\frac{mv^2}{2}](https://tex.z-dn.net/?f=qV%3D%5Cfrac%7Bmv%5E2%7D%7B2%7D)
![v=\sqrt{\frac{2qV}{m}}](https://tex.z-dn.net/?f=v%3D%5Csqrt%7B%5Cfrac%7B2qV%7D%7Bm%7D%7D)
and we know
Force due to magnetic field will Provide centripetal Force
![qvB=\frac{mv^2}{r}](https://tex.z-dn.net/?f=qvB%3D%5Cfrac%7Bmv%5E2%7D%7Br%7D)
![B=\frac{\sqrt{\frac{2Vm}{q}}}{r}](https://tex.z-dn.net/?f=B%3D%5Cfrac%7B%5Csqrt%7B%5Cfrac%7B2Vm%7D%7Bq%7D%7D%7D%7Br%7D)
and B is equal for both particles
thus ![\frac{m}{r^2}=constant](https://tex.z-dn.net/?f=%5Cfrac%7Bm%7D%7Br%5E2%7D%3Dconstant)
![\frac{m_1}{r_1^2}=\frac{m_2}{r_2^2}](https://tex.z-dn.net/?f=%5Cfrac%7Bm_1%7D%7Br_1%5E2%7D%3D%5Cfrac%7Bm_2%7D%7Br_2%5E2%7D)
![r_2^2=\frac{4.8}{2.2}\times 8^2](https://tex.z-dn.net/?f=r_2%5E2%3D%5Cfrac%7B4.8%7D%7B2.2%7D%5Ctimes%208%5E2)
![r_2=11.81 cm](https://tex.z-dn.net/?f=r_2%3D11.81%20cm)