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Question
Is p − E/c valid for electrons?
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Solution
From Einstein's mass- energy equation,
`E = mc^2`
⇒ `E = (m_0c^2)/sqrt(1-v^2/c^2)`
Relativistic momentum ,
`p = mv`
⇒ `p = (m_0c^2)/sqrt(1-v^2/c^2)`
Combining the above equations, we get :
`E^2 = m_0^2c^4 + p^2c^2`
From the above equation, it is clear that for p = E/c to be valid, the rest mass of the body should be zero. As electrons do not have zero rest mass, this equation is not valid for electrons.
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