lesson Science Reader NO 3 class Third year

lesson : Science Reader NO. 3 class : Third year –scientific Section Baktheer Secondary School prepared by the teacher: Mohammed Attass ( abu attass )

light / vocabulary 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. act like Angle of incidence Angle of reflection Behave Combination Concave Convex Diverge Split vacuum 11. Converge 12. Edge 13. refraction 14. Effect 15. Emit 16. Focus 17. Lens 18. Outer space 19. Transparent 20. Medium 21, . physicists 22. Quantum theory

1. Definitions Light is a form of energy. Over the years physicists have had different ideas about how light behaves. First some said it acts like a steam of particles. Later others observed that light is like a wave that can travel through a vacuum , such as our space. Most recently , the quantum theory has stated that it is a combination of both.

Reflection. 2 We see an object : a. When an object emits light. ( like in a bulb ) b. When an object reflects ( like in a mirror ) c. When an object changes light passing it. (in a prism ) we see most things by reflection.

2. Reflection There are two types of surfaces a smooth surface and a rough surface. The smooth white surface reflects more light than the rough black one because in smooth surfaces the angle of the incidence is the same as the angle reflection. Click here On a rough black surface these angles are different because rough surfaces scatter light.

Put a spoon at an angle in a glass of water It appears to bend because light waves appear to bend when they pass from one transparent medium to another ( a ir and water ).

Refraction is made use of commonly in lenses. Lenses are specially –shaped pieces of glass that reflects light exactly. There are two types of lenses a convex lens and a concave lens.

* A convex lens ? A convex lens that is thicker in the middle than at the edge and it makes objects look smaller. It converges rays.

A concave lens is a lens that is thinner in the middle than at the edge and makes objects look larger. It diverges rays.

Types of lenses Rays are converged in convex lenses

Refraction in prism Click here

Questions A. Number these definitions in the historical order. 1. Light is a combination of particles and waves. ( ) 2. Light is a series of waves. ( ) 3. Light is a stream of particles. ( )

Answer these questions B. 1. Which sort of lens would be more useful for reading glasses ? Why ? a convex lens would be more useful for reading glasses because it makes objects look larger. 2. You must stand in front of a mirror to see your reflection. The glass in a mirror acts like a smooth surface so reflects maximum light.

ese statements : 3. Leaves are sometimes burnt by sunlight passing through raindrops on the leaves. Raindrops serve as a convex lens. 4. When you look at yourself in the bowl you look smaller. Why ? The bowl of a spoon is concave. 5. When you look at yourself in the back you look biiger. Why ? The back of spoon is convex.

Discussion 1. What is our source of natural light ? The sun 2. When does a raindrop act like a prism ? The sun shines passing through it, creating rainbow. 3. When do use lenses ? When we want to make objects look smaller or larger.

What is the difference between reflection and refraction? n Reflection is when light is bounced back at an object. Refraction is when light is bent as it travels through a different medium, but continues in the same general direction n

Prism reflects light passing through it by: Mohd attass Bakatheer Secondary school