page 17 24. Which row in the table describes the conduction band and the gap between the conduction band and the valence band in an insulator? Conduction band Gap between conduction band and valence band A unfilled bands overlap B full bands overlap C unfilled large gap D full small gap E full large gap 25. Astronomers use the following relationship to estimate the mass M of a galaxy 2 v r M G  where v is the orbital speed of a star in the outer regions of the galaxy, in m s−1 r is the orbital radius of the star, in m G is the Universal Constant of Gravitation. A star orbits at a radius of 4.0 × 1020 m in the outer regions of the Triangulum galaxy. The orbital speed of the star is 120 km s−1. Based on this information, the mass of the Triangulum galaxy is: A 3.8 × 1020 kg B 7.2 × 1032 kg C 8.6 × 1034 kg D 7.2 × 1035 kg E 8.6 × 1040 kg. [END OF QUESTION PAPER] page 18 SPACE FOR ROUGH WORK page 19 SPACE FOR ROUGH WORK page 20 [BLANK PAGE] DO NOT WRITE ON THIS PAGE