Cathode Ray Tube Experiment - J.J. Thomson

Biography of a Nobel Prize Winning Physicist - J.J. THOMSON

1. Group Activity On Biography Of A Nobel Prize Winning Physicist – J.J.Thomson Submitted to : Dr. N.L. Mathakari Dr. A.B. Deore Submitted by : Mr. Anish Agarwal (101018) Mr. Aditya Agarwal (101019) Mr. Akkahshh Agarwaal (101020) Mr. Anshul Agarwal (101021) MIT-WORLD PEACE UNIVERSITY , KOTHRUD PUNE - 411038

2. SIR JOSEPH JOHN THOMSON Birth : 18 December 1856 in Manchester , England . Father - antique bookshop Mother – family’s textile company Brother - two years younger than him. Wife : Rose Paget and had one son and one daughter . Age 14 – Owens College ( now University Of Manchester ) Age 20 – Trinity College, Cambridge to obtain B.A. (Mathematics) , M.A. (Mathematics). Education And Personal Life

3. Career Age 28 – Cavendish Professor Of Physics at University of Cambridge . Nobel Prize in 1906 – Conduction of electricity by gases . Lectures at Princeton And Yale University – Discharge of electricity through gases Discovered the electron Elected as a Fellow of the Royal Society thomson (Th) – unit of mass-to-charge ratio JJ Thomson Avenue – University of Cambridge campus Various awards and honors – Adams Prize, Franklin Medal, etc.

4. The Cathode Ray Tube Experiment : Discovery of the electron Cathode ray tubes are sealed glass tubes which have been evacuated to create vacuum . A high voltage is applied at the two pieces of metal at one end of the tube which causes a beam of particles to flow from the cathode to the anode. The tubes are called “cathode ray tubes” because the particle beam originates at the cathode. The ray is detected by painting a special coating of phosphorus onto the other end of the tube. It emits light when impacted by cathode ray. What is the ray made up of ? Does the ray have electrical charge ? To test it’s properties, Thomson placed two oppositely charged plates around the cathode ray. Instead of going straight through, the ray was deflected away from the negatively – charged plate and it was attracted towards the positively – charged plate . Thomson also placed two magnets on either side of the tube and observed the same result.

5. The results helped him to determine the mass-to-charge ratio of the particles. He repeated the experiments using different metals and found that the properties of the cathode ray remained constant irrespective of the metal used . Thomson made the following CONCLUSIONS from his experiment : The cathode ray is composed of negatively charged particles . The particles that make up cathode rays are a 1000 times smaller than hydrogen atom. All different metals give off cathode rays. Atoms have tiny, negatively charged particles inside them – “ ELECTRONS ” On the whole, atoms are electrically neutral. Hence, there must be positive charge in the atom to balance out the electrons. This lead to the Plum Pudding Model of an Atom . The Cathode Ray Tube Experiment : Discovery of the electron

6. Contributions Highly gifted teacher. Six research assistants - Nobel Prize in physics Two research assistants - Nobel Prize in chemistry . Son , George Paget Thomson - Nobel Prize in physics - proved the wave-like properties of electrons . 1905 - natural radioactivity of potassium . 1906 - hydrogen has a single electron per atom . Invention of Mass Spectrometer . Measuring size of nanoparticles and hence calculate density of particle leading to finding the properties and behavior of the particle. Looking for toxins (DEG-Diethylene Glycol) in toothpaste. Looking for pesticides in food . Atom as a Plum Pudding – famous but incorrect model – uniformly spread and positively charged pudding with electrons embedded in it.

7. BIBLIOGRAPHY https://en.Wikipedia.org/wiki/J._J._Thomson https://www.famousscientists.org/j-j-thomson/ https://www.nobelprize.org/nobel_prizes/physics/laureates/1906/thomson-facts.html