Question

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

• A. If the Assertion and Reason are true and Reason is the correct explanation of Assertion
• B. If both Assertion and Reason are true but Reason is not the correct explanation of Assertion
• C. If Assertion is true but Reason is false
• D. If both Assertion and Reason are false

Answer 1

Answer: (B)

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.