Who evaluated the mass of electron indirectly with help of charge:
- Thomson
- Millikan
- Rutherford
- Newton
The Correct Option is B
Solution and Explanation
To determine who evaluated the mass of an electron indirectly with the help of charge, we need to look into historical experiments that measured the electron's charge and mass.
The correct answer to this question is Millikan.
Explanation:
Robert A. Millikan is renowned for his oil drop experiment, conducted around 1909, which famously measured the charge of an electron. This experiment allowed Millikan to calculate the electric charge of single electrons, which in turn enabled the indirect determination of the electron's mass when combined with other measurements.
- Millikan's Oil Drop Experiment:
- Millikan suspended tiny charged oil droplets between two metal electrodes and balanced them using an electric field to counteract gravitational force.
- By adjusting the electric field's strength and observing the droplets' behavior, he calculated the charge on an electron.
- Once the charge \( e \) was determined, and with the already known charge-to-mass ratio of the electron from previous experiments by J.J. Thomson, the mass of the electron could be calculated as: \[ m = \frac{e}{\frac{e}{m}} \] where \( \frac{e}{m} \) is the charge-to-mass ratio.
Why Other Options Are Incorrect:
- Thomson: J.J. Thomson measured the charge-to-mass ratio (\( \frac{e}{m} \)) of the electron using cathode rays, but did not directly measure the charge or mass separately.
- Rutherford: Ernest Rutherford is best known for his discovery of the nucleus and nuclear model of the atom, not for measuring the electron's mass or charge.
- Newton: Isaac Newton’s works are largely focused on classical mechanics and optics, having no direct involvement with the electron's mass or charge evaluation.
Thus, Robert Millikan played a key role in indirectly evaluating the mass of an electron through his precise measurements of its charge. This breakthrough was a significant step in the field of atomic physics.
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