What is the weight of light?

Answer 1

very light ...why do you think they called it light in the first place

Answer 2

"Light" is a form of energy.

Light exhibits two natures, a wave-like nature and a particle like nature.
A semi-common question is asked as to what the weight of a single photon is (a photon being the particle nature of light).

A photon travels at the speed of light. In order for this to be possible, a photon must have zero rest mass....in other words it is weightless, if not, it could never achieve the speed of light.

A photon carries with it a very specific amount of energy depending on the wavelength of the light. Since the photon has energy, but no rest mass, it instead has momentum.

If one adds the often omitted momentum component of the E = mc^2 equation back in and then neglect the part which deals with rest mass, one would get,
E = pc
Where E is the energy, p is the momentum, and c is the speed of light in a vacuum.

Using Planks equation,
E = hv,
where E is again the energy, h is Plank's constant, and v is the frequency of the light, one can find the photon's energy and then substitute back into the earlier equation to find its momentum.

Answer 3

Weight means it is under some acceleration eg in a gravity field. Weight in a gravity field depends on the field strength of the field.

Mass however is the same where ever it is, its the measure of stuff if you will. So I'll talk about mass here.

You can get a lump of light called a photon, and the energy of that photon is given by

e=hf

where h is Planck's constant
f is the frequency of the incident light

Coupling this equation with e=mc^2 we get

hf=mc^2

Rearanging:

m=hf/c^2

The mass of the photon is directly proportional to the frequency of the light with the constant being h/c^2.

So, to kind of answer your question, the mass of light (photon) is dependent on the frequency of the light you are massing.

Answer 4

It weighs in the same manner as does the human soul. And yes, it does exist and I am not making this up. The human body loses weight at the moment of death and can only be explained by the soul escaping the confines of the body. Same weight logically applies to light.

Answer 5

Previous responders are not correct. The equivalent mass of a photon is given by its energy, divided by the square of the speed of light, in accordance with Einstein's theory of special relativity. It is obvious that the mass equivalent of a photon is small.

Answer 6

light is quite light-weight... light weighs very very little... however light can be diffracted because light can be different colors... light is measured in quanta... because light is energy that is measured in terms of frequency and wavelength... light can be affected by the force of gravity... because light can't escape the gravitational forces of massive black holes... light is electromagnetic radiation that is measured in photons... and photons of light are massless particles that have no weight

Answer 7

I dont kno wats its weight but i'm sure it does have mass, anythin that can travel has its presence got to have weight - basic rule of nature or Physics

Answer 8

the weight (actually the correct term would be "mass") of light is a variable dependant on it's frequency.

Answer 9

Actually, it has a weight. As energy is mass.

Too tired to do the calculation, but take the energy of a single photon at light speed (duh), then use E = mc^2 to derive mass.

Answer 10

light has no weight, it's a wave of energy...

Answer 11

light has no weight it travels trough mass