• Best of luck to the class of 2024 for their HSC exams. You got this!
    Let us know your thoughts on the HSC exams here
  • YOU can help the next generation of students in the community!
    Share your trial papers and notes on our Notes & Resources page
MedVision ad

How to prove light is a particle by experiment (1 Viewer)

MumboJumboNo5

New Member
Joined
Mar 23, 2003
Messages
10
Location
Western Sydney
Would an experiment involving a cathode ray tube (with a paddle inside) be an experiment to show how light can be composed of particles?

Are cathode rays a type of light?? Or is there another experiment I could perform myself to verify the particle nature of light.

The experiment I'm speaking of is the one where the cathode ray tube was connected to a power source and then after switching the power on a ray is emitted inside the tube, making the paddle wheel spin. IE, ray has momentum, thus implies the ray has mass and must therefore be composed of particles.

Hm, thanks wholely for any help.
 
N

ND

Guest
Cathode rays are a stream of electrons, and as such are particles. I don't know about an experiement you could do to support the particle theory, maybe something with the photoelectric effect?
 

+:: $i[Q]u3 ::+

Jaded Member
Joined
Apr 28, 2003
Messages
898
Gender
Female
HSC
2003
the cathode ray with the paddle wheel shows that electrons are particles (with mass, and hence momentum).

ND's right; use the photoelectric effect.
Eg Hertz's experiment; when UV light was shone on the receiver loop, the spark jumped the gap more easily. This is the photoelectric effect, and it only happens because the photons transfer their energy in discrete "packets" to the electrons. This also happens in the cathode ray tube.

you can also talk about what happens to the current when u increase the frequency/intensity etc of the light.
 

Affinity

Active Member
Joined
Jun 9, 2003
Messages
2,062
Location
Oslo
Gender
Undisclosed
HSC
2003
The photoelectric effect just shows that light energy come in discrete "packets".
Whether it follows that it is a particle or not depends on your definition of a particle.
And the cathode ray experiments are about electrons, not light
 

Halo

Member
Joined
Nov 28, 2002
Messages
52
Location
Heaven.
Gender
Undisclosed
HSC
N/A
Please bear in mind that electrons have a wave-particle duality nature. The electron microscope, for example, exploits this property.

And the paddle wheel experiment shows cathode rays (electrons) has momentum, hence mass (not the other way around :)).
 
B

Bambul

Guest
Actually, if you consider the speed of light as an identity of infinity, then they could have zero mass. By multiplying zero by infinity you could end up with some amount of momentum.

Now where's my Nobel Prize for Physics? :)
 

Affinity

Active Member
Joined
Jun 9, 2003
Messages
2,062
Location
Oslo
Gender
Undisclosed
HSC
2003
Please bear in mind that electrons have a wave-particle duality nature. The electron microscope, for example, exploits this property.
Actually the electron microscope would work better if particles aren't waves, because then the smallest dimension that can be measured need not be larger than the wavelength of the electron. ;)

Actually, if you consider the speed of light as an identity of infinity, then they could have zero mass. By multiplying zero by infinity you could end up with some amount of momentum.
1.) infinity is not an ordinary number, you can't mutliply it with 0. it's just some lame word which physicist use to sweep problems under the carpet
 
Last edited:

f001error

New Member
Joined
Jun 17, 2003
Messages
26
remember a wave is a moveing distrubance, thus to have a wave ya be needing something to disturb. thus ye can have particles with a wave running through them
 

Affinity

Active Member
Joined
Jun 9, 2003
Messages
2,062
Location
Oslo
Gender
Undisclosed
HSC
2003
what do EM waves disturb though?

don't get me wrong I actually agree with f001error. I believe everything that exists is a disturbance of the 'vaccum'
 

Lazarus

Retired
Joined
Jul 6, 2002
Messages
5,965
Location
CBD
Gender
Male
HSC
2001
EM waves are self-propagating... rather than 'emerging' from sequential disturbances of particles, as normal waves do...

I'm not sure how you'd explain EM waves via the conventional definition... in fact, I'm not really sure why they're called waves in the first place... they're more like a group of moving electric/magnetic fields... perhaps they shouldn't be classed as waves...

It's been a while since I've done this. :)
 

f001error

New Member
Joined
Jun 17, 2003
Messages
26
ethier maybe...oh wait they got rid of that theory...err well it has to be distrubing something ta be a wave
 

Users Who Are Viewing This Thread (Users: 0, Guests: 1)

Top