2.1 Discovery of Sub-atomic Particles

Question 1

Name the sub-atomic particles.

Answer 1

electrons, protons and neutrons

Question 2

Electrons were discovered by whom and using which experiment?

Answer 2

By J.J. Thomson using Cathode Ray Discharge Tube experiment.

Question 3

What was the condition inside cathode ray tube?

Answer 3

Low pressure and high voltage.

Question 4

Explain the nature of cathode rays.

Answer 4

• Cathode rays consist of negatively charged particles
• Cathode rays move from cathode to anode
• The characteristics of the cathode rays do not depend upon the nature of the gas present in the cathode ray tube.

Question 5

According to Thomson, the amount of deviation of the particles from their path in presence of electrical and magnetic field depends upon which factors?

Answer 5

Charge, Mass and Voltage
- Higher the charge, greater is the deflection
- Higher the mass, lower is the deflection
- Higher the voltage, greater is the deflection

Question 6

What is the charge by mass (e/m) ratio of an electron?

Answer 6

1.758 x 10^11 C/kg

Question 7

Charge on an electron by determined by whom?

Answer 7

R.A. Millikan

Question 8

Protons were discovered by whom and using which experiment?

Answer 8

By E. Goldstein using Cathode Ray Discharge Tube experiment (modified).

Question 9

Explain the nature of canal rays or anode rays.

Answer 9

• Canal rays consist of positively charged particles
• Canal rays move from anode to cathode
• The characteristics of the canal rays depend upon the nature of the gas present in the cathode ray tube.

Question 10

What is the charge by mass (e/m) ratio of a proton?

Answer 10

9.67 x 10^7 C/kg

Question 11

Neutrons were discovered by whom and using which experiment?

Answer 11

By James Chadwick using Beryllium bombardment with alpha particles experiment.