E/M of positive rays

1. Thomsons parabola method

1.1. New Topic

1.2. Potential between anode and cathode - cathode (perforated) and is cooled by a jacket - positive beam is produced - subjected parallel to Electric and Magnetic field - Electric field is (perpendicular to the positive ray beam) x = k1 XE/Mv2 - Magnetic Field is applied y = k2 Be/Mv - The combined action of Electric and Magnetic Field - y2/x = (k2 2 /k1 × B2/X) × E/M - Thus E/M is a constant - y 2/ x is a constant and is the equation of parabola. To determine E/M - measure x and y and B and X to be known. Limitations - Intensity of the parabolic trace is low due to velocity dispersion, No blurring , no accuracy in measurements and The secondary rays makes the analysis difficult

2. Aston's Mass Spectrograph

2.1. The steam of positive ions ontained from a discharge is rendered into a fine beam passing it between

3. Dempster Mass spectrograph

4. POSITIVE RAYS ( properties ) They are deflected by the presence of magnetic and electric field in their path They are produced from the anode They comprise of positively charged particles . Later Thomson, Aston and Dempster discovered the positive rays through their experimen

5. Determination of isotope - The graph is drawn between current and potential. B fixed , V changes hence current is recorded. The number of isotopes determined with number of peaks - height high, current high, more ions, material has coating of anode. Thomson's Parabola Method DemAston's Mass spectrograph pster's Mass spectrograph