What is Light? ( IB Physics - Atomic Physics )

Have you ever wondered what light was all about? This video, produced for IB Physics and A-Level students provides you with a clear presentation of the following topics:

_ A description of the electromagnetic spectrum,

_ Light combines properties of waves and particles (photons) so it is both at the same time.

_ Photons carries discrete amounts of energy that can be absorbed or emitted by atoms.

Presented by Edouard Reny, PhD in solid state chemistry, and private tutor in physics for international high school students.

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[kirteepurohit]

Your explanations are very clear. They are short simple and very understandable, the animations help too.
You explain very calmly which really help to digest the knowledge you deserve more subscribers and views

[LECityLECLEC]

Your physics explanations are beautiful!

[faceman]

The light beam from torch was helpful. I trying to work out if the light from sun comes from sun in a long wave and we see just part of the visible wave lengths. OR like the torch it only gives produces a wave of the visible part of light.

[sunitarawat]

First of all thank you a lot
Sir i am in class 8th and i am very curious to know about light, my doubt is that a photon with different frequency has different amount of energy in it, I mean different photons can have different different amount of energy??

[vidyamalla]

Sir what makes something wave or particle? I mean how exactly we can differentiate wave and particle?

[Qqaswd]

Would this state that photons are a “pure form of energy” or “energy in its purest form” im not sure if I can quite wrap my head around that yet lol

[dennyoconnor]

Light is not a particle.
The photoelectric effect of metal surfaces is due to the quantization of atomic electron orbitals not the EM light wave. The impinging EM wave (light) pumps the electron. The electron absorbs energy and moves faster until it pops free of the outer orbital shell of that atom and moves away. That is the photoelectric effect.
SInce electron shell orbitals are quantized the electron released has an energy that matches a specific orbital. The EM radiation (light) that pumped the electron is not quantized and energy was absorbed by the electron until it gained enough energy to break free.
Now, there is a threshold to the energy required to pump the electron so the EM light wave has to contain at least that minimum energy (frequency) to do the job. If the light is below the threshold (lower frequency) the electron will not break free.
If the impinging EM light wave is significantly higher in energy (higher frequency) than the threshold it will pump the electron to go free.
If both the outer shell orbital electrons of the metal and the impinging light were quantized (i.e. tuned to a specific frequency) then as the energy/frequency of the impinging EM light wave rose higher and higher (rising frequency of light) fewer and fewer electrons would be released because the quantum levels would no longer be matched - the impinging light "photons" and the orbital electrons no longer tuned to resonance)
Given that we know that does not happen and given that we know that the orbital shell electrons are quantized and given that we know there is a minimum frequency of light waves needed to release the outermost electrons, and given that we know that photo electron release continues as the frequency of the impinging light increases we know that light is not a particle but a continuous EM wave.
Since we know that light radiates from metals when they are heated (filaments in the physics lab) and that the light changes color as the heat (energy) increases or decreases we know that when the heat is increasing the metal is releasing EM waves of higher energy/frequency from the orbital shell electrons that pump up and fall back in response - and vice versa for decreasing heat.
The changing color of light radiated as the temperature of a metal is changed is due to the quantization of the orbital shell electrons that pump up and fall back in discrete steps - and is not due to the quantization of electromagnetic light energy.
Everything we know about EM waves in the radio wave bands carries through to the light wave bands. There is not separate physics for the two bands of EM waves.

[vidyamalla]

Is speed of light just a phrase for value 3*10^8 m or does it have any other significance?

[moaazelgarhikhalifa]

"High frequency" Warm regards,
I cannot understand the relationship between an opening size and the wavelength that can go through
Example:
The microwave oven, why radiations can't penetrate the small openings in its door?
And why the electrons in the metal of that openings net does not reradiat outside?!
Why walls absorbs light but allow radio waves to go through? How is this physically happening?

[shashwatsingh]

Sir can we visualise Photon as a particle with a wave like tale, similar to the structure of (spream). sir please reply....I am confused.

[AdarshKumar-gqbw]

Can u please explain why the maximum KE of ejected photo electron doesn't depend on the Intensity of incident photon...please...

[fabiolaprasetyo]

Does "light" (Do photons?) also make up atom (since any substance emits light when excited)? Thanks in advance

[scottdellrobinson]

A byproduct of nuclear fission? Idunno

[chickylord]

Let's imagine we are inside a room, there is no electricity, no light, and no windows, there is only one door to enter and exit from. In the room, there are three pipes on the walls that are like faucets. The first has active magma flowing down from it. Can you see the magma? The flow of the magma is stopped and the next faucet is turned on. It has molten iron flowing from it. Can you see it? The second faucet is turned off and the third one is turned on. Molten glass flows from it. Can you see it? That is also turned off. Remember that the room has no electricity and no light, it is completely pitch black. Will these illuminate their surroundings? If the answers to these questions are yes or no, could you scientifically explain how and why?

[kr_]

Can u put light on microscope? and see what it is made of?

[SoimulPatriei]

A wave is a disturbance that travels through a medium. For example, typically the air is the medium that carries the sound waves. Perhaps the property common to all particles is that they can be counted. A thing cannot be both a wave and a particle. I've found it always misleading to say that the light is both a particle and a wave.

[samratmanandhar]

Does it mean that if there is no light electron can't revolve it's neutron? What happens when atom gains or lose energy? It really made me confused.

[simongross]

I think that light is an optical illusion