![Periscope: [Cont.] The periscope consists of two parallel plane mirrors (or prism) . Could you guess at what angle should each mirror (or prism) be placed ? Why ? Which type of periscope is better ? Mirror or prism ? Why ?](https://image.slidesharecdn.com/reflectionoflight-100829070425-phpapp02/85/Reflection-of-light-34-320.jpg)
![4. The diagram below shows the position I of the image formed by a plane mirror of an object O. (a) Continue the two rays drawn leaving O to show how they would be reflected at the mirror. [2] GCE ‘O’ LEVEL Nov 1995 I O](https://image.slidesharecdn.com/reflectionoflight-100829070425-phpapp02/85/Reflection-of-light-39-320.jpg)
![4.(b) I is a virtual image. Explain the meaning of this. [2] (Cont. …) Q. 4 Nov 1995 Since the image, I, is produced by the reflection of light and cannot project on a screen, there- fore it is a virtual image.](https://image.slidesharecdn.com/reflectionoflight-100829070425-phpapp02/85/Reflection-of-light-40-320.jpg)
Reflection of light
- 1. REFLECTION OF LIGHT REFLECTION OF LIGHT
- 2. Objectives Define the terms normal, angle of incidence and angle of reflection State the angle of incidence is equal to the angle of reflection and use this principle in construction, measurements and calculations.
- 3. Nature of light A form of energy which enables us to see It travels in straight line It travels at a very high speed (3.0 x 10 8 ms -1 ) in vacuum. It is emitted by luminous sources such as SUN, STARS, CANDLES, LAMPS, etc.
- 4. Nature of light White light is a mixture of seven different colours namely Red, Orange , Yellow, Green, Blue, Indigo, Violet. Light is a transverse wave and forms part of the electromagnetic spectrum .
- 5. Light ray The path along which light energy travels is called a RAY. It is represented by a straight line with an arrow to show its direction of motion.
- 6. Beam of Light A beam of light is a bundle of light rays. Parallel beam Converging beams Diverging beams
- 7. Reflection of light The abrupt change in the direction of propagation of light rays that strike the boundary between different medium.
- 8. Normal : plane normal normal center An imaginary line perpendicular to a surface where the reflection occurs.
- 9. Reflection of Light(1) i r Incident ray normal plane mirror The ray striking the surface (incoming ray) The ray reflected from the surface (outgoing ray) Reflected ray
- 10. Reflection of Light(2) The angle between incident ray and normal The angle between reflected ray and normal i = angle of incidence r = angle of reflection i r i r Incident ray normal plane mirror Reflected ray
- 11. Laws of Reflection: Law 1: The incident ray, the reflected ray and the normal at the point of incidence all lie on the same plane. Law 2: The angle of incidence is equal to the angle of reflection. Angle i = Angle r
- 12. The diagram shows a ray of light being reflected by a plane mirror MN. Which one of the following statements is completely correct ? A LP is the incident ray, PR is the reflected ray and x is the angle of reflection. B LP is the reflected ray, x is the angle of incidence and y is the angle of reflection. C LP is the incident ray, x is the angle of incidence and y is the angle of reflection. D PQ is the normal, x = y, and PR is the incident ray. C Example 1
- 13. Reflection by the plane mirror i r Plane mirror Note: Normal always perpendicular to the mirror i r Incident ray normal plane mirror Reflected ray i = angle of incidence r = angle of reflection i r
- 14. The diagram shows a ray of light reflected in a plane mirror. What is the angle of reflection? Example 2 Angle incidence = 90 0 - 40 0 = 50 0 Angle of reflection = Angle of incidence = 50 0
- 15. A ray of light is reflected from a plane mirror as shown in the diagram below: What is the angle of incidence? What is the size of the angle marked b ? Example 3 Angle of incidence = 90 0 - 10 0 = 80 0 Angle b = 10 0
- 16. The diagram shows a ray of light striking a plane mirror. What is the angle of incidence if the total angle between the incident ray and reflected ray is 70 ? Example 4 Angle of incidence = Angle of reflection = 70 0 / 2 = 35 0
- 17. Example 5 In the figure below, ray AB will be reflected twice. Find the angle of reflection in the second reflection. Copy the figure and complete the path of the ray. angle r 1 = 30 0 ; angle r 2 = angle i 2 = 90 0 - 30 0 = 60 0 30 0 r 1 i 2 r 2 30 0 A B
- 18. MIRROR IMAGE(1) BIKE BOOK BOX CHOKE DECIDE CHICK
- 19. MIRROR IMAGE(1) BIKE BOOK BOX CHOKE DECIDE CHICK
- 20. MIRROR IMAGE(2) SPEED POLES BED LIGHT POWER CHECK
- 21. MIRROR IMAGE(2) SPEED POLES BED LIGHT POWER CHECK
- 22. Formation of images on a plane mirror: To the eye, all the reflected rays appear to have come from I, the image. Thus, the image formed is virtual.
- 23. Real and Virtual Images A real image is one which can be formed on a screen. It is produced by ray that converge at the position of the image. A virtual image is one which cannot be formed on a screen. It is produced by reflection of light.
- 24. Image formed by Plane Mirror: It is virtual. It is upright. It is lateral inverted. It has the same size as the object. Distance of the image from the mirror is equal to the distance of the object from the mirror.
- 25. A person stands 2.0 m in front of the mirror as shown. How far from the person is her image? Example Image is 4.0 m from the person.
- 26. The diagram shows two divergent rays of light from an object O being reflected from a plane mirror. At which position will the image be formed? Example B
- 27. i r Note: i = r object image normal eye object image mirror mirror Ray diagram showing the formation of an image
- 28. Image formed by the plane mirror
- 29. Plane mirror Regular reflection Black surface Absorption Irregular surface Diffuse reflection Glass block Transmission Glass Various cases of rays:
- 30. Two types of Reflection: 1. Regular reflection ( Image formed by plane, a smooth surface, image can see by our eyes)
- 31. 2. Diffuse reflection ( Image formed by white paper, with rough surface. Image formed usually not clear) (continue …)
- 32. mirror mirror Periscope: Periscopes are used in submarines so that people below the water surface can see what is happening above. (Type 1)
- 33. prism prism Periscopes are used in submarines so that people below the water surface can see what is happening above. Periscope: (Type 2)
- 34. Periscope: [Cont.] The periscope consists of two parallel plane mirrors (or prism) . Could you guess at what angle should each mirror (or prism) be placed ? Why ? Which type of periscope is better ? Mirror or prism ? Why ?
- 35. GCE O-Level Past Examination Paper Science (Physics)
- 36. November 1989 8 . Which of the following correctly describes the image formed in a plane mirror when compared to the object? A virtual smaller B virtual same size C virtual larger D real same size B
- 37. Nov 1990 6. An object ‘O’ is placed in front of a plane mirror. A viewer looks into the mirror as shown in the diagram. In which position is the image of O formed? B
- 38. Nov 1991 10. The diagram shows a ray of light being reflected by a plane mirror MN. Which one of the following statements is completely correct ? A LP is the incident ray, PR is the reflected ray and x is the angle of reflection. B LP is the reflected ray, x is the angle of incidence and y is the angle of reflection. C LP is the incident ray, x is the angle of incidence and y is the angle of reflection. D PQ is the normal, x = y, and PR is the incident ray. C
- 39. 4. The diagram below shows the position I of the image formed by a plane mirror of an object O. (a) Continue the two rays drawn leaving O to show how they would be reflected at the mirror. [2] GCE ‘O’ LEVEL Nov 1995 I O
- 40. 4.(b) I is a virtual image. Explain the meaning of this. [2] (Cont. …) Q. 4 Nov 1995 Since the image, I, is produced by the reflection of light and cannot project on a screen, there- fore it is a virtual image.