Directions for: The questions consist of two statements each, printed as assertion and reason. While answering these questions you are required to choose any one of the following five responses A. If both the Assertion and the Reason are true and the Reason is a correct explanation of the Assertion. B. If both the Assertion and the Reason are true but the Reason is not a correct explanation of Assertion. C. If the Assertion is true but the Reason is false. D. If both the Assertion and the Reason are false. E. If Assertion is false but Reason is true.
Assertion: Mass of moving photon varies inversely as the wavelength. Reason: Energy of the particle = mass \[\times \] (speed of light)2.A) A
B) B
C) C
D) D
E) E
Correct Answer: B
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 loses an amount \[\Delta M\] of mass, an equivalent amount \[\Delta E\] of energy is produced given by \[\Delta E=\Delta m{{c}^{2}}\] .....(1) where c is speed of light. This is called Einstein mass-energy relation. Also energy \[\left( E \right)=hv\] 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, \[E=\frac{hc}{\lambda }\] \[\Rightarrow \] \[E\propto \frac{2}{\lambda }\] ??(2) From Eqs. (1) and (2), mass of photon varies inversely as the wavelength.
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