Q.Write any five properties of cathode rays.

Cathode rays, discovered in low-pressure discharge tubes, are streams of fast electrons and display a set of characteristic properties — straight-line travel, negative charge, deflectability by fields, momentum, and the ability to cause fluorescence and produce X-rays.

Origin

When a high voltage is applied between two electrodes sealed in a glass tube containing gas at very low pressure, a stream of radiation is found to emanate from the cathode (negative electrode) and travel towards the anode; this radiation is called cathode rays. J.J. Thomson later established that cathode rays consist of fast-moving electrons.

Properties (any five)

1. Travel in straight lines: Cathode rays travel in straight lines from the cathode, and cast sharp, well-defined shadows of any opaque object placed in their path.

2. Negatively charged particles: They are deflected towards the positive plate when passed between two oppositely charged parallel plates, showing that they consist of negatively charged particles (electrons).

3. Deflected by magnetic fields: They are also deflected by a magnetic field, in a direction consistent with Fleming's left-hand rule for a negative charge in motion.

4. Possess momentum and kinetic energy: Cathode rays can set a small, light paddle wheel placed in their path into rotation, and can heat a metal target on which they fall — showing that they carry momentum and kinetic energy, i.e. they consist of material particles, not simply radiation.

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