IB Physics SL B.1.15 Apparent Brightness

Practise distinguishing how bright a star appears from its intrinsic luminosity or absolute magnitude and explaining differences through distance or combined light from multiple…

Syllabus
First assessment 2025
Objective
—
Level
SL

Exam points

  • define apparent brightness as received power per unit area or how bright a star appears from Earth
  • explain equal apparent magnitude with different luminosity by comparing the stars' distances
  • combine the received brightness of unresolved binary components when explaining a system's appearance

B.1.15—Apparent brightness question 1

[Maximum number: 1]

Alpha Centauri A and B form the closest binary star system to the Earth. This binary star system is the third brightest stellar object in the night sky.

Arcturus is the fourth brightest star in the night sky. Its apparent brightness is slightly greater than that of the star Alpha Centauri A.

Outline why the binary star system Alpha Centauri appears brighter than Arcturus.

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