已知氢原子从基态激发到某一定态所需能量为 10.20 eV,当氢原子从能量为-0.85 eV的状态跃迁到上述定态时,所发射的光子的能量为[ ]
A. 2.55 eV
B. 3.41 eV
C. 4.25 eV
D. 9.95 eV
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在气体放电管中,用能量为12.09 eV的电子去轰击处于基态的氢原子,此时氢原子所能发射的光子的能量只能是[ ]
A. 12.09 eV
B. 10.2 eV
C. 12.09 eV,10.2 eV和 1.89 eV
D. 12.09 eV,10.2 eV和 3.4 eV
At present, the biggest amount of currency in the global international settlement is()
A. JPY
B. EUR
C. USD
D. GBP
传统的国际贸易和结算中的信用主要是()两类。
A.系统信用和银行信用
B.系统信用和司法信用
C.商业信用和司法信用
D.D.商业信用和银行信用
In the case of other conditions unchanged, which of the following currency settlement the importer should choose ()
A. have down trend of currency
B. have up trend of currency
C. the value is fixed currency
D. currency fluctuates up and down significantly