Q3 of 40 Page 4

What is phosphorescence? How does it differ from fluorescence?

Phosphorescnece is a phenomenon in which certain substances like zinc salts, radium salts etc., glow, emitting visible light when they are irradiated either with X-rays or ultraviolet rays. The glow continues even after the source of light is cut off.
Fluorescent substances also emit light in the visible region when light falls on them. But they do not glow after the source of light is cut off where as phosphorescent substances continue emitting light under the same condition.

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1 a) What is the charge and mass of the anode rays emitted when, hydrogen gas is enclosed in the discharge tube experiment? What is the name of these particles?
b) Do the anode rays always consist of protons whatever be the gas enclosed in the discharge tube? Explain. 2 a) What is the other name of X-rays?
b) How are x-rays produced? Why was this name given?
c) How are x-rays made tools in diagnostic purposes in the medical field? 4 a) Who discovered the nuclear model of the atom?
b) Explain how Rutherford's atomic structure cannot explain the stability of atom? 5 Explain how Bohr's atomic model explains the emission and absorption of radiation.