P.1 Book 3A Section 1.1 Light rays Light rays How an object is seen? Light beams and light rays Ray diagrams Check-point Light rays

P.2 Book 3A Section 1.1 Light rays Light rays Beams of sunlight shine pass the edges of the trees. Can you tell how light travels from this photo?

P.3 Book 3A Section 1.1 Light rays 1 How an object is seen? Luminous objects: e.g. candle flames give out light by themselves emit light in all directions We can see an object when light from the object enters our eyes.

P.4 Book 3A Section 1.1 Light rays 1 How an object is seen? Non-luminous objects: e.g. the moon, books, human beings do not give out light by themselves visible only when they reflect light shining on them into our eyes

P.5 Book 3A Section 1.1 Light rays 2 Light beams and light rays Scientists introduce the ray model to study the behaviours of light: “Light consists of narrow rays travelling in straight lines.” Light travels in straight lines.

P.6 Book 3A Section 1.1 Light rays 2 Light beams and light rays Light beam: a stream of light represented by sets of lights Parallel beam

P.7 Book 3A Section 1.1 Light rays 2 Light beams and light rays Divergent beam

P.8 Book 3A Section 1.1 Light rays 2 Light beams and light rays Convergent beam

P.9 Book 3A Section 1.1 Light rays 3 Ray diagrams Many light rays from the point of objects enter our eyes. We can just show only two rays in a ray diagram. They mark out a cone of rays from the point.

P.10 Book 3A Section 1.1 Light rays 3 Ray diagrams To indicate that the eye sees the whole object, two cones of rays are drawn from the two ends of the object to the eye. Use an arrow to represent the object.

P.11 Book 3A Section 1.1 Light rays 3 Ray diagrams Light rays from a near point are divergent. The object moves away from the eye  the rays become less divergent The rays emitted from a distant point are parallel.

P.12 Book 3A Section 1.1 Light rays Check-point 1 – Q1 Which of the diagrams correctly shows the path of light for us to see a book? A B C

P.13 Book 3A Section 1.1 Light rays Check-point 1 – Q2 A Only 4 rays of light from the pen can reach the eye. B The eye can see the whole pen. C Only the two ends of the pen are luminous. D The pen emits converging light beams. Which of the following is the best description of the figure?

P.14 Book 3A Section 1.1 Light rays The End