(a) State two properties of cathode rays. (b)... | WAEC SSCE - Physics - 2001

Question 1 Report

(a) State two properties of cathode rays.

(b) Explain how the intensity and energy of cathode rays may be increased.

Answer

(a) Two properties of cathode rays

They travel in straight lines from the cathode and cast sharp shadows of objects placed in their path.
They are streams of negatively charged particles (electrons), so they are deflected by both electric and magnetic fields (towards the positive plate).

Other acceptable properties: they carry energy and momentum, they produce heat and fluorescence on striking a screen, and they can produce X-rays on hitting a metal target.

(b) Increasing the intensity and energy of cathode rays

Intensity (number of electrons per second) is increased by raising the filament (heater) current. A hotter cathode emits more electrons by thermionic emission, so the beam current and hence the brightness increase.

Energy (speed of each electron) is increased by raising the accelerating potential difference between the cathode and the anode. Each electron gains kinetic energy \(eV\) as it is accelerated, so a larger anode voltage gives faster, more energetic electrons.

Read lesson note on Properties Of Waves: Reflection, Refraction, Diffraction (WAEC)

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Answer Details

(a) Two properties of cathode rays

They travel in straight lines from the cathode and cast sharp shadows of objects placed in their path.
They are streams of negatively charged particles (electrons), so they are deflected by both electric and magnetic fields (towards the positive plate).

Other acceptable properties: they carry energy and momentum, they produce heat and fluorescence on striking a screen, and they can produce X-rays on hitting a metal target.

(b) Increasing the intensity and energy of cathode rays

Read lesson note on Properties Of Waves: Reflection, Refraction, Diffraction (WAEC)

Read lesson note on Structure Of The Atom (Nigeria Only) (WAEC)

Properties Of Waves: Reflection, Refraction, Diffraction

Structure Of The Atom (Nigeria Only)

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(a) State two properties of cathode rays. (b) Explain how the intensity and energy of cathode rays may be increased.

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