Karteikarten
Modern Physics
Karten in diesem Stapel (21)
- 1Give Three Properties of Electrons.1. They orbit the Nucleus
2. They are negatively Charged
3. The charge on the electron is the smallest amount of charge found in nature - 2What is thermionic Emission?Thermionic Emission is the giving off of electrons from the surface of a hot metal
- 3How does a cathode tube operate?1. A current is passed through the heating coil, causing it to heat the cathode which in turn causes electrons to be emitted
2. Because of the high potential difference between the cathode and anode the electrons are accelerated across the tube towards the anode. As a result a current flows in the circuit
3.Electrons which pass through the hole in the middle of the anode continue on until they hit the fluorescent screen.
4. The stream of electrons can be deflected by electric or magnetic fields, which are generated from the X and Y plates.
5.The voltage on the Y-plates is adjusted to make the cathode rays move up or down.
6.The voltage on the X-plates is adjusted to make the cathode rays move left or right. The result is that the rays can move across the computer or television screen. - 4What are cathode rays?Cathode rays are streams of high-speed electrons moving from the cathode
- 5What is the formula for ‘work done in moving electron = gain in kinetic energy’eV=1/2mv^2
e-charge on an electron
m-mass on an electron
eV=loss/gain in potential energy - 6What is an electronvolt?The electronvolt (eV) is the energy lost or gained by an electron when it accelerates through a potential difference of one volt.
- 7How do electrons move when at right angles to a magnetic field?A beam of electrons moving at right angles to a magnetic field will move in a circular path
- 8Give 2 applications of a cathode ray tube1. Cathode Ray Oscilloscope
2. It also forms the main component in (old-style) televisions and computers - 9What are X-rays?X-rays are produced when high-energy electrons collide with a high density target.
- 10How does an X-Ray tube work?1.The low voltage supplies power to a filament which in turn heats the cathode at A.
2.Electrons are emitted from the hot cathode due to thermionic emission.
3.They get accelerated across the vacuum due to the very high voltage and smash into the high-density anode (usually tungsten) at B.
4.Most of the kinetic energy gets converted to heat, which must be removed with a coolant.
5.Some inner electrons in the tungsten get bumped up to a high orbital, then quickly fall back down to a lower lever, emitting X-rays in the process.
6.These X-rays are emitted in all directions.
7.Most of these get absorbed by the lead shielding, but some exit through a narrow window, where they are then used for the required purpose. - 11What is X-ray production the opposite of?The photoelectric effect
- 12Name 3 properties of X – rays1. They are Electromagnetic Waves
2. They cause ionisation of atoms
3. They have high penetration powers - 13Give 2 uses of X-rays1. Medicine: To detect broken bones
2. Industry: To detect breaks in industrial pipes - 14What is the photoelectric effect?The Photoelectric Effect is the emission of electrons from a metal due to electromagnetic radiation of a suitable frequency falling upon it.
- 15What is a photocell?This is a device which conducts electric current due to electromagnetic radiation of a suitable frequency falling upon it.
- 16How is the photocurrent related to the intensity of light?The photocurrent is directly proportional to the intensity of light
- 17What is the threshold frequency?For a given metal the frequency below which photoemission will not occur is called the threshold frequency.
- 18What is the work function of a metal?The minimum energy needed to remove the loosest electron from the surface of that metal metal
- 19What is a photon?A photon is a packet of electromagnetic radiation
- 20Give 2 applications of the photoelectric effect1. Burglar Alarms
2. Automatic doors - 21—
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- Leaving Certificate Physics Karteikarten am Modern Physics, erstellt von bardini daley am 05/05/2020.
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- bardini daley
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