- #1

Lizwi

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2) From this equation E=PC , does this mean E of a photon is 0 because P must be zero since it depends on mass?

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- Thread starter Lizwi
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In summary, the energy of a photon can be found using the equation E= \frac{\hbar c}{\lambda }. While an observer in relative motion with a photon may perceive it as having relative mass, photons are actually massless.

- #1

Lizwi

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2) From this equation E=PC , does this mean E of a photon is 0 because P must be zero since it depends on mass?

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- #2

clamtrox

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Lizwi said:

2) From this equation E=PC , does this mean E of a photon is 0 because P must be zero since it depends on mass?

Remember that classical mechanics does not work for things moving at the speed of light. You need to use special relativity instead. Just because something has zero mass doesn't mean that its momentum needs to be zero.

- #3

- #4

Mark M

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Lizwi said:

2) From this equation E=PC , does this mean E of a photon is 0 because P must be zero since it depends on mass?

Hi Liziwi,

The equation for finding the energy of a photon is

[tex]E= \frac{\hbar c}{\lambda }[/tex]

Where E is energy, [itex]{\hbar }[/itex] is Planck's constant, [itex]c[/itex] is the speed of light, and [itex]{\lambda }[/itex] is the wavelength of the light.

Also, because E=mc

- #5

ZikZak

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Mark M said:Also, because E=mc^{2}, an observer in relative motion with a photon will perceive it as havingrelativemass.

Really? What experiment does he employ to perceive this "mass" of a photon?

- #6

Mentz114

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Mark M said:... an observer in relative motion with a photon will perceive it as havingrelativemass.

All observers are always in motion wrt to light with speed c. Photons are massless.

Special relativity is a theory proposed by Albert Einstein in 1905, which explains the relationship between time, space, and motion. It states that the laws of physics are the same for all observers in uniform motion, and the speed of light is constant in all inertial frames of reference.

According to special relativity, the rest mass of a photon is always zero. This means that a photon, which is a particle of light, does not have any mass when it is at rest. However, it has energy and momentum, which is dependent on its frequency and wavelength.

No, the rest mass of a photon cannot be measured because it is always zero. This is a fundamental property of photons, and no experiment or technology can change this fact.

The rest mass of a photon is directly related to its speed, as the speed of light is the maximum possible speed in the universe. Since the rest mass of a photon is zero, it travels at the speed of light in a vacuum, which is approximately 299,792,458 meters per second.

Yes, special relativity can be applied to particles with rest mass. However, the theory predicts that as an object approaches the speed of light, its mass will increase, and time will slow down for that object. This phenomenon is known as time dilation and is a fundamental concept of special relativity.

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