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YOOKUNG
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I want to know that light has mass or not.
็ำHelp me ! Can you explain little?
็ำHelp me ! Can you explain little?
Rasalhague said:The FAQ doesn't mention that a system of more than one photon, not all traveling in the same direction, can have an invariant mass, since we can define a frame in which the vector sum of their momenta is zero, and in this frame, its (nonzero) energy will equal its invariant mass.
There is only one definition of invariant mass.Rasalhague said:whether a photon has invariant mass depends on which of two currently used definitions of invariant mass you use
DaleSpam said:There is only one definition of invariant mass.
Rasalhague said:It's inevitable that, as a student learns more physics, they have to trade in some of the simplified definitions they're given at first for more refined and general definitions. It just gets a bit dizzying when that whole process is compacted into one paragraph! "Mass is defined thus," with no explicit statement that this is not a general definition, or what special case it's restricted to (a particle with mass), followed immediately by "or more generally..."
ZapperZ said:Don't you think this gets very confusing for someone JUST trying to learn something simple, especially if we have to do this for every single thing we talk about? Do you see constant qualifier for the Photoelectric effect that this is strictly applicable ONLY for single-photon photoemission without any appreciable Schottky effect? Which is more "dizzying"?
thecritic said:Nope. But it does have momentum!
magpies said:Only one answer is acceptible here
Rasalhague said:Re [itex]E^2 = (pc)^2 + (m_0 c^2)^2[/itex]
"All of the photon's energy is in the term [itex]pc[/itex].
Vanadium 50 said:Only one answer is correct here.
This is a common question that has been debated for centuries. The answer is that light does not have mass as we traditionally define it. Mass is a measure of an object's resistance to acceleration, and since light has no rest mass, it cannot be accelerated or slowed down. However, light does have energy, which can exhibit some properties of mass.
Scientists have used various experiments and observations to determine that light has no mass. One of the most famous experiments was conducted by Albert Michelson and Edward Morley in the late 1800s, which showed that the speed of light is constant regardless of the observer's frame of reference. This led to the development of Einstein's theory of relativity, which explains the relationship between energy, mass, and the speed of light.
While light itself has no mass, it can still be affected by gravity. According to Einstein's theory of general relativity, gravity is not a force but rather a curvature of spacetime caused by massive objects. Since light follows the curvature of spacetime, it can be affected by the gravitational pull of massive objects, such as stars and black holes.
Light interacts with matter through the electromagnetic force. Light is made up of tiny particles called photons, which have both wave and particle-like properties. When light comes into contact with matter, the photons can be absorbed, reflected, or scattered, depending on the material's properties.
While light does not have mass, there is evidence that it does have energy, which can exhibit some properties of mass. For example, the bending of light around massive objects, such as stars, is evidence of its energy-mass equivalence. Additionally, experiments have shown that photons can have momentum and exert pressure, further supporting the idea that light has energy and can behave similarly to mass in certain situations.