Photoelectric Effect Grade 12 Physical Science Revision Notes:
The photoelectric effect is the process that occurs when electromagnetic radiation (light) shines on a metal surface and ejects electrons from the metal. In order to understand the photoelectric effect and spectra, we need to remind ourselves of Bohr’s atomic model.
Photoelectric Effect Grade 12 Notes pdf
Background on Photoelectric Effect Grade 12 Physical Science
Around the turn of the twentieth century, it was observed by a number of physicists (including Hertz, Thomson and Von Lenard) that when light was shone onto a metal plate, electrons were emitted by the metal. This is called the photoelectric effect.
The characteristics of the photoelectric effect were a surprise and a very important development in modern Physics. To understand why it was a surprise we need to look at the history to understand what physicists were expecting to happen and then understand the implications for Physics going forward.
Important Terms for Photoelectric Effect Section
- The photoelectric effect is the phenomenon where the light of a particular frequency causes electrons to be ejected from a metal surface.
- The dual nature of light – light can be explained in two ways; light having a wave nature and light having a particle nature.
- Work function – the minimum energy package needed to eject an electron from a metal surface. Threshold frequency – the minimum frequency of light needed to eject an electron from a metal surface
- Photon – energy package of a specific electromagnetic radiation, also called a quantum of energy.
- Electromagnetic radiation – Radiation that consists of wave-like electric and magnetic fields in space, including white light (red, orange, yellow, green, blue, indigo, violent), microwave, radio signals and x-rays. Electromagnetic radiations with higher frequencies are useful to mankind as some, like violent light, can be used to kill bacteria. Violent light is used mainly in killing bacteria in butcheries.
- Planck’s constant (h) – a constant used in calculating the energy of a photon. h = 6,63 x 10 -34 J.s
- Ground state: electron or atom in its lowest possible energy state, most stable state
- Excited state (or activated state): electron or atom in a higher energy state than its ground status, unstable
- Quantum: a specific (indivisible) amount (usually of energy), plural: quanta
Video Lesson: Photoelectric Effect Grade 12
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