Atoms and Quanta - test

1. Which of the the following provides experimental evidence for the existence of energy levels in atoms?
A Excited gases emit spectral lines of discrete frequencies
B In an X-ray tube there is a short wavelength related to the p.d. across the tube
C In the Millikan oil drop experiment the drop occasionally undergoes abrupt changes in velocity
D No photoelectrons are emitted from a given surface if the frequency of the incident light is less than a certain value
E The number of secondary electrons ejected from metal surfaces by incident particles of given energy depends upon the metal

 

2
A
B
C
D
E

 

 

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