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When a hydrogen atom going from n=2 to n=1 emits a photon, its recoil speed is x5 m/s. Where x= . (Use, mass of hydrogen atom =1.6 10-27 kg)
17
Photon energy: E=13.6 (1- 14 )=10.2 eV
Momentum conservation: mv=pphoton= Ec
v= Emc= 10.2 1.6 10-191.6 10-27 3 108
=3.4 m/s= 175 m/s
x=17
Answer: 17
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