This image provided by the Direction of Penal Centers of El Salvador shows an x-ray taken of one of four prisoners at a maximum security Salvadoran prison in Zacatecoluca, 35 miles southeast of the capital of El Salvador. Four cellular telephones were found in the intestines of as many prisoners in El Salvador's maximum-security prison, authorities said Wednesday, Sept. 6, 2006. The discovery happened Tuesday at the prison in Zacatecoluca after suspicious prison officials took x-rays of each of the prisoners, prison spokesman Jaime Villanova said. (AP Photo/Centros Penales)
The short answer is "no", but it is a qualified "no" because there are odd ways of interpreting the question which could justify the answer "yes". Light is composed of photons so we could ask if the photon has mass. The answer is then definitely "no": The photon is a massless particle. According to theory it has energy and momentum but no mass and this is confirmed by experiment to within strict limits. Even before it was known that light is composed of photons it was known that light carries momentum and will exert a pressure on a surface. This is not evidence that it has mass since momentum can exist without mass. [ For details see the Physics FAQ article What is the mass of the photon? ]. Sometimes people like to say that the photon does have mass because a photon has energy E = hf where h is Planck's constant and f is the frequency of the photon. Energy, they say, is equivalent to mass according to Einstein's famous formula E = m
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