CHEMISTRY · Multi-part · CBSE · Chemistry · Structure of Atom · Structure of Atom
Problem
In a classroom demonstration, a hydrogen discharge tube emits light that is passed through a prism, producing a series of bright, colored lines on a screen. One of the prominent lines is measured to have a wavelength of 486 nm.
(a) Describe the difference between an emission spectrum and an absorption spectrum, and explain the physical processes that produce each type.
(b) The laboratory technician states that the 486 nm line belongs to the Balmer series and occurs when an electron in a hydrogen atom changes from a higher energy level to the level with principal quantum number n=2. If sunlight passes through a cool cloud of atomic hydrogen before reaching an observer on Earth, would the 486 nm line appear as a bright line or a dark line in the observed solar spectrum? Justify your answer in terms of atomic energy-state changes.
(c) A simplified reference list of Balmer-series transitions is reproduced below.
• 656 nm : transition n=3→2
• 486 nm : transition n=4→2
• 434 nm : transition n=5→2
Using only the information in the list, identify the initial and final principal quantum numbers for the 486 nm line and explain how the wavelength data support your identification.