page 11 14. The following statement represents a nuclear reaction. 240 236 4 94 92 2 Pu U He   The total mass of the particles before the reaction is 398.626 × 10−27 kg. The total mass of the particles after the reaction is 398.615 × 10−27 kg. The energy released in this reaction is: A 1.1 × 10−29 J B 3.3 × 10−21 J C 5.0 × 10−13 J D 9.9 × 10−13 J E 3.6 × 10−8 J. 15. The irradiance of light incident on a surface from a point source is 20.0 W m−2. The distance between the point source and the surface is 5.0 m. The point source is now moved to a distance of 25.0 m from the surface. The irradiance of the light incident on the surface is now: A 0.032 W m−2 B 0.80 W m−2 C 1.2 W m−2 D 4.0 W m−2 E 100 W m−2. [Turn over