Do photons have angular momentum?

Question

Isnt Plank's constant a unit of angular momentum?

Answer 1

yes, photons have angular momentum.

and yes Planks constant is a unit of angular momentum.

angular momentum is L = mvr --> mass*velocity*distance -->kg*(m/s)*m = kg*m^2/s

Planks const. is J*s -->kg*(m^2/s^2)*s = kg*m^2/s

Answer 2

Plank's constant is, and at the same time, is not a unit of angular momentum.

Plank's constant has units of J * s / Photon.
The Joule Second can be re-written as the SI unit for angular momentum.
1 Joule = 1 kg m^2 / s^2
So 1 J s = 1 kg m^2 / s, which is the same as the unit of angular momentum (since the radian is not really an SI unit).

A photon's actual, linear momentum (as opposed to the quantum value of a particle's angular momentum) is given by,
p= E / c
where p is the momentum, E is the photon's energy, and c is the speed of light in a vacuum.
Of course, a photon's energy is given as,
E = hv
where E is the energy, h is plank's constant, and v is the frequency of the light.

Answer 3

Inquisitive should check the units of angular momentum. Momentum times a distance (angular momentum) has the same units as force times distance times time, which is Js, just like Planck's constant.

Also, the intrinsic angular momentum of the photon is, indeed 1 Planck unit (hbar), but this means that there are 2*1+1 possible states corresponding to m=-1,0, or 1. So it is possible to detect and angular momentum of 0 in a particular direction.

Answer 4

Yes, photons do have linear and angular momentum.

Though Planck's constant has the the same units as angular momentum (N m s - Newton meters second), it is not a unit of angular momentum.

Search for: circular polarized light angular momentum
There are many other pages devoted to this topic than those listed below.

Answer 5

Planck's Constant is NOT a unit of angular momentum. It has units of energy x time (J*s. or eV*s usually).

Yes photons have angular momentum. They have angular momentum in two ways. One, as an external observer, you can find the angular momentum using the classical L = r x p, where L, r, p are vectors representing angular momentum, postion from center of rotation, and linear momentum respectively. The 'x' here means vector cross product.

But that's not the interesting angular momentum. The interesting angular momentum is the intrinsic angular momentum called "spin." Spin is a quantum mechanical property of particles, that is analogous to the particle spinning like a top, but isn't really that since that would require particles to have volume (which they don't). So it's just a property of particles that is related to angular momentum.

The photon has a spin of 1. It can be plus or minus 1, but is always 1.

Electrons, protons, neutrons, and their anti-particles have spin plus or minus 1/2. The photon's spin 1 makes it a boson (integer spin) and the electrons, etc are fermions (with half-integral spin). All elementary particles can be classified into one of these two categories (never both). They behave different ways due to these spin values, in particular Fermions follow the Pauli Exclusion Principle. If you're interested in quantum mechanics and elementary particles, I would read up on these topics.

EDIT:

The units on Planck's constant are the same as the units of angular momentum, but having the same units doesn't mean it is an angular momentum quantity. It's more of a conversion/scale factor than a "unit of angular momentum." Wikipedia describes it as "units of action," a reference to Lagrangian formalism.

Now about the spin of a photon: "Photons mediate the electromagnetic interaction; they are the gauge bosons of quantum electrodynamics (QED), which is a U(1) gauge theory. Photons have total spin 1 (in units of ), and follow Bose-Einstein statistics, making them bosons. A massive spin-1 particle has three possible spin states (−1, 0 and +1; the projection of spin in a particular direction). However, in the framework of special relativity, this is not the case for massless spin-1 particles, such as the photons. They have only two spin projections (namely -1 and +1), or helicities, which correspond to the right- and left-handed circular polarizations of classical electromagnetic waves. Linear polarizations are produced by the superposition of the two spin projections of a photon.

Since virtual photons are not constrained to move at c, they may have spin projection 0."
(from wikipedia)

Answer 6

Yes, Plank's constant is in units of angular momentum.

"Quantum theory prescribes that spin angular momentum can only occur in certain discrete values. These discrete values are described in terms of integer or half-integer multiples of the fundamental angular momentum unit h/2p, where h is Plank's constant. "

Answer 7

Photons are traditionally reported to be massless. it truly is a verify of speech that physicists use to describe something about how a photon's particle-like houses are defined by technique of the language of particular relativity. The photon does have mass! in spite of everything, it has power and power is equivalent to mass. Photons do no longer have a relax mass, inspite of the undeniable fact that it really is okay because photons by no skill relax - they're continually shifting about with their same power = frequency = mass.

Answer 8

I would add something here, but there are a lot of smart people who pretty much covered it all above.