You\'ve heard of anti-matter, right? Well, the electron\'s anti-particle is call

Question

You've heard of anti-matter, right? Well, the electron's anti-particle is called the positron. When an electron and a positron at rest annihilate, their rest energy is converted into a pair of photons, both photons having the same energy (this has to be true in order to conserve both energy and momentum). What is the wavelength of the photons (to three significant digits)?

2.43×1012 meters. 8.09×1021 meters. 7.27×104 meters. 3.86×1013 meters. 7.72×1013 meters. 1.93×1013 meters. None of the above

Explanation / Answer

Here ,

mass of electron , me = 9.109 *10^-31 Kg

let the wavelength of the photon

2 * h * c/wavelength = 2 *me * c^2

6.626 *10^-34 * 3 *10^8/wavelength = 9.109 *10^-31 * (3 *10^8)^2

solving

wavelength = 2.425 *10^-12 m

the wavelength of the photon is 2.43 *10^-12 m

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