The diagram shows a simple cathode ray tube - Leaving Cert Physics - Question d - 2009
Question d
The diagram shows a simple cathode ray tube. Thermionic emission occurs at plate A.
(i) What is thermionic emission?
(ii) What are cathode rays?
(iii) Why is ther... show full transcript
Worked Solution & Example Answer:The diagram shows a simple cathode ray tube - Leaving Cert Physics - Question d - 2009
Step 1
What is thermionic emission?
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Answer
Thermionic emission is the process by which electrons are emitted from a material, typically a hot metal, when it is heated sufficiently. This occurs due to the thermal energy overcoming the binding energy of the electrons in the metal.
Step 2
What are cathode rays?
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Cathode rays are streams of electrons that are emitted from the cathode (negative electrode) in a vacuum tube. They travel at high speeds towards the anode (positive electrode) when a high voltage is applied.
Step 3
Why is there a high voltage between A and B?
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The high voltage between A and B is required to accelerate the electrons emitted from plate A towards plate B. This acceleration increases the kinetic energy of the electrons, allowing them to travel efficiently through the tube.
Step 4
What happens to the cathode rays when they hit the screen C?
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When the cathode rays hit the screen C, they are converted to light, producing a visible image. This occurs because the energy of the electrons is transferred to the phosphorescent material on the screen, causing it to emit light.
Step 5
Give a use for a cathode ray tube.
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A cathode ray tube is commonly used in televisions and computer monitors, as well as in oscilloscopes and X-ray devices. They convert electrical signals into visual images.
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