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Q. Assertion Mass of moving photon varies inversely as the wavelength. Reason Energy of the particle = mass x (speed of light)2

VMMC MedicalVMMC Medical 2011

Solution:

Einstein by his theory of relativity proved that mass and energy are related to each other and every substance has energy due to its mass also. If a substance losses an amount $ \Delta M $ of mass, an equivalent amount $ \Delta E $ of energy is produced given by $ \Delta E=m{{c}^{2}} $ ?(i) where, c is speed of light. This is called Einstein. mass-energy relation. Also energy E = hv ... (ii) where h is Plancks constant and v is frequency Also, $ v=-\frac{c}{\lambda }, $ where c is speed of light and $ \lambda $ is wavelength. Hence, $ E=\frac{hc}{\lambda } $ $ E\propto \frac{1}{\lambda } $ From Eqs. (i) and (ii), mass of photon varies inversely as the wavelength.