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13.Nuclei
easy
A ${\pi ^0}$ at rest decays into $2\gamma $ rays ${\pi ^0} \to \gamma + \gamma $. Then which of the following can happen
A
The two $\gamma 's$ move in same direction
B
The two $\gamma 's$ move in opposite direction
C
Both repel each other
D
Both attract each other
Solution
Since a $\pi$ meson is at rest initially, thus the initial momentum of the system is $zero$.
So, from law of conservation of linear momentum, the final momentum of the system must also be $zero$.
To do so, the two gamma rays must move in opposite direction to each other so that the total momentum of the system remains zero after the reaction.
Standard 12
Physics
