Assignment 1
Discovery of elementary particles and atomic models
1. Explain Thomson experiment (3 experiments, how he discover the electron and his proposed atomic model. Is this model accepted as the correct atomic model? Why? (20)
2. In Thomson’s experiment, the potential difference of a cathode tube is 250 V, the magnetic field used in the experiment is 5×10-2 Tesla, and with known electrical charge and mass, calculate (a) The velocity of electron at anode. (5) (b) The radius of electron beam when travelling perpendicular through the magnetic field. (5) (c) Find the magnitude of the electric field that needs to be applied in order to turn the electron beam into a straight path again. (5)
3. Explain Rutherford experiment and the difference between Rutherford’s and Thomson’s model. Which model is the most believable at that time? (15)
4. Calculate the de Broglie wavelength for an electron moving at 1×107 m/s (5)
5. Describe in detail about the current atomic model. (10)
Note: You can search for more information about particular atomic models from the internet. Extra points will be awarded for answers that are not in the lecture. You MUST, however, put the reference for your answer.