Reflection and refraction of light .pptx

reflection and refraction of light for prep 2

1. A Journey into the World of Optics" Reflection and refraction of light Ms. : Marina George Grade 8

2. *What is always found on the ground but never gets dirty ? A shadow flashlight

3. Introduction: What is light ? light is a form of energy that travels in waves. Light is electromagnetic wave

4. Reflection of light It is the rebounding (returning back ) of light waves in the same medium on meeting a reflecting surface.

5. Types of light reflection Regular or uniform reflection Irregular or non-uniform reflection Examples ? Examples ? *A plane mirror *A thin sheet of aluminum *A stainless steel sheet *A leaf of a tree *A piece of paper *Wool

6. It is a narrow light beam which is r epresented by a straight line, it intersects with the reflecting surface at the point of incidence It is a narrow light beam which is represented by a straight line, it is reflected from the reflecting surface at the point of incidence It is the angle between the incident light ray and the line perpendicular to the reflecting Surface at the point of incidence It is the angle between the reflected light ray and the line perpendicular to the reflecting Surface at the point of incidence Point of incidence Concepts related to light reflection

7. *when light reflects on a surface, its reflection is ruled by two important laws. Activity 1 Virtual lab : https://phet.colorado.edu/sims/html/bending-light/latest/bending-light_all.html Conclusion : The reflection of light is governed by two laws: Angle of incident = angle of reflection The incident light ray, the reflected light ray and the normal all locate in one plane perpendicular to the reflecting surface.

8. Now put on your thinking cup and think with me ? 1) W.H? Light ray falls perpendicular on a reflecting surface. Ans. It will reflect on itself ,that because the angle Of incident and angle Of reflection are equal zero

9. 1) Find the angle ( r ) in the opposite figure. Assessment

10. ASK ME QUSETIONS SCAN THE QR CODE ,PLEASE

11. Break 2 min.

12. Light refraction *Work in groups to discuss answer to this question. be ready to share your ideas with the rest of the class . 1) List as many transparent materials as you can. Try to include solids, liquids and gases . Light refraction: It is the change of light path when it travels from a transparent medium to another transparent medium of different optical density

13. Similarly, as light travels from: * The ability of the transparent medium to refract the light is called : (Optical density of the medium) * they are arranged according to optical density as follows glass> water>air The change of speed can cause the light to change direction.

14. Angle of incidence: It is angle between the incident light ray and the normal at the point of incidence on the interface. Angle of refraction: It is the angle between the refracted light ray and the normal at the point of incidence on the interface Angle of emergence: It is the angle between the emergent light ray and the normal at the point of emergence on the interface Concepts related to light refraction

15. Activity 2 Virtual lab : https://phet.colorado.edu/sims/html/bending-light/latest/bending-light_all.html Conclusion : The refraction of light phenomenon occurs when the light ray travels from a transparent medium to another transparent medium of different optical density.

16. Laws of light refraction 1) Light passing from water or glass into air : The light speeds up the light passing from glass or water into air is bent away from the normal the angle of refraction is greater than the angle of incidence. 2)Light passing from air into water or glass : The light slows down The light passing from air into glass or water is bent towards the normal . the angle of incidence is greater than the angle of refraction.

17. Now put on your thinking cup and think with me ? 1) W.H? Light ray falls perpendicular to the interface between two different transparent media. Ans. It will pass without refraction. The angle of incidence is equal to the angle of refraction equal zero. ∠i = Angle of incidence = 0°  , ∠e = Angle of emergence =

18. Refraction in everyday life * Refraction can be a nuisance. It can stop you from seeing clearly through wet windows. Each individual drop of water on the window refracts light in a different direction, making it very difficult to see. This is why many vehicles have windscreen wipers. The windscreen wipers remove the water drops. It is then easier to see clearly as all the refraction from the glass is in the same direction. * Refraction can also be useful. Lenses are used in our eyes, in cameras and in glasses that people wear, to cause refraction of light. A lens is a curved piece of glass that is designed to refract light in a known way.

19. https:// quizizz.com/join?gc=67119477 Quiz time Join Game 1.Use any device to open : 2 . Enter this code(------- ) (the teacher will give you the code ) Or Scan QR code

20. Thank you