Hydrogen Emits Light at Certain Discrete Frequencies

question 37

Multiple Choice

Hydrogen emits light at certain discrete frequencies. One particular emission has a frequency of 4.57 × 10¹⁵ s^-1, as measured in the frame of reference of the hydrogen atom. Light from this emission is observed coming from a star that is moving away from Earth at 0.900c. What is the observed frequency? Note that, in addition to time dilation, one must take into account that successive wavefronts have to travel longer distances because the star is moving away (Doppler Effect) .

• A) 1.99 × 10¹⁵ s^-1
• B) 7.62 × 10¹⁵ s^-1
• C) 1.99 × 10¹⁶ s^-1
• D) 1.05 × 10¹⁵ s^-1
• E) 0.90 × 10¹⁵ s^-1

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Definitions:

Littoral Zone

the part of a sea, lake, or river that is close to the shore, where sunlight penetrates to the bottom enabling plant growth.

Limnetic Zone

The limnetic zone is the open and well-lit area of a freshwater body, such as a lake or pond, away from the shore, where photosynthesis can occur, supporting a variety of aquatic life.

Benthic Zone

The ecological region at the lowest level of a body of water, including the sediment surface and some sub-surface layers.

Canadian Lake

A lake located in Canada. The term can refer to any of the thousands of lakes within the Canadian territory known for their natural beauty and ecological significance.