it is easier to explain by using diagram

real image


virtual image

for spm candidates, try to get ur add math and physic A if u wanna pursue in engineering field...

good luck to u all

@igmroey - integration is quite ez, esp for the volume part.. i cant remember did f5 learn how to integrate volume by rotating the graph on certain axis?if yes, i just wanna share my way of solving the question.. u just need to identify the radius from the equation.. let say u wanna rotate the graph on X-axis for sure u need to make the equation to y=mx+c since Y is the radius for the graph(unless using shell method which u will learn in university)

and for prob distribution once u can imagine the diagram just like raptor did, i can say it is a free mark question ;D..