A level physics photoelectric effect

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Mavs04
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Hi,
I don’t completely understand the second bullet point on the ppt slide, I’m not sure what the relationship is between the intensity of an EM wave and it’s energy, but I know that when it behaves as photons their energy is independent to the intensity.
Of someone could explain why lots of electrons would be emitted at high intensities no matter the frequency that would be great!


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Sinnoh
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High intensity means that there are lots of photons being emitted. The more photons emitted, the more total energy is being sent to the metal.

When considering the energy of an individual photon, yes intensity is irrelevant. When considering the total energy from the radiation, then you need to take into account how many photons there are.
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Mavs04
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(Original post by Sinnoh)
High intensity means that there are lots of photons being emitted. The more photons emitted, the more total energy is being sent to the metal.

When considering the energy of an individual photon, yes intensity is irrelevant. When considering the total energy from the radiation, then you need to take into account how many photons there are.
Thanks,
Yeah in this topic we’re looking at the energy of individual photons because each liberates a single electron, but I don’t really get how the intensity is related to the energy of the EM radiation when it’s behaving as a wave - I thought the energy of waves was linked to their amplitude?
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Sinnoh
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(Original post by Mavs04)
Thanks,
Yeah in this topic we’re looking at the energy of individual photons because each liberates a single electron, but I don’t really get how the intensity is related to the energy of the EM radiation when it’s behaving as a wave - I thought the energy of waves was linked to their amplitude?
This is why photons are weird.

The energy of an individual photon is linked to its frequency (or wavelength, depending on which form of the equation you use) and nothing else.

EM radiation in this example consists of many photons, each with their own specific energy. The sum of the energies of all the photons is the energy of the EM radiation. The more intense the radiation is, the more photons there are. The more photons there are, the higher the energy, simply because there are more photons there. That's why higher intensity means higher energy in this case. Just like how the Sun releases more energy than a candle even if the light they emit has roughly the same wavelength.

The amplitude of photons themselves isn't something you really consider, since they are quantum-mechanical.
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Eesa268
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Anyone help on this question?
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