Read Positronium: Replace Mass with Reduced Mass
This short read prepares one exact NSEP pattern: bohr scaling for positronium. Identify the physical condition before calculating.
Bohr Scaling for Positronium is the central idea in this question pattern. Identify the condition in the stem before applying the method below.
Start with the physical model
Read the configuration once, state the conserved quantity or governing law, and mark any changing geometry, sign convention or limiting condition.
Build the relation
Hydrogen energy and radius depend on the reduced mass. For positronium, the electron and positron have equal mass m, so µ=m/2, whereas hydrogen has µ≈m.
The individual electron speed about the common centre of mass is not equal to the hydrogen Bohr speed. Thus A and C are correct.
Check before selecting
Check units, sign and one limiting case. A valid result must still fit the original geometry and stated constraint.
OlympIQ exam lens
- ✓Name the governing law before using a formula.
- ✓Keep the stated geometry and direction information explicit.
- ✓Use one unit or limiting-case check.
Using electron mass in place of reduced mass misses both the energy and radius scaling.
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