Gwenno dims a lamp as far as the dial goes. In the wave picture there is no smallest piece of light: the stream just gets smoothly weaker, forever. The photoelectric effect said otherwise.
The last topic ended on a broken model: energy arriving as a continuous, spread-out wave could not explain what light does to a metal plate. This lesson states the model that can. You have seen light described as an electromagnetic wave; what changes here is how its energy arrives.
Light delivers its energy in separate whole lumps.
A source emits light one entire lump at a time, and a surface absorbs light one entire lump at a time.
There is no half-lump. Nothing ever emits or absorbs a fraction of one.
A photon behaves as a particle of light: a separate, countable thing that arrives whole.
Describing light as a stream of photons is called the photon model.
Dim Gwenno's lamp far enough and the photons arrive as individual lumps, one at a time, rather than a smooth stream.
The dimmest possible flash of one kind of light is a single photon. Below one photon there is nothing to send.
A lamp is dimmed until its beam is barely there. In the photon model, what reaches the wall?
Light delivers its energy in separate whole lumps: photons.
Dimming the lamp lowers how many photons leave it each second.
Each photon that does arrive is still one whole lump.
Individual whole photons arrive, one at a time, with gaps between arrivals.
A sheet of dark material absorbs light from a faint beam. Can it take in half of one photon's energy?
Light is absorbed only one entire lump at a time.
A photon is one whole lump: there is no half-lump to take.
So the sheet absorbs each photon's whole energy, or none of it.
No. The sheet absorbs each photon whole, or not at all.
In the photon model, how does light deliver its energy to a surface?
Bodhi says: 'Light is emitted and absorbed only one entire photon at a time.' Is Bodhi correct?
A single whole lump of light energy is called which of the following?
Which statement is the photon model of light?
A faint beam of one kind of light shines on a screen in a dark room. In the photon model, what does the screen receive?
A material absorbs light from a beam. How much energy can one absorption event take in?