ENERGY Reflection of light Myanmar

Introduction Objectives: Able to identify regular and diffuse reflection Able to explain the laws of reflection Able to construct the devices that use the concepts of reflection of light Target group: Secondary level (Grade-7) Duration/Mode: 2 periods (1hour 30 mins) /student-centred

Reflection of Light Why can’t we see objects in the dark? Because there is no light. Light falls on the object. Light is sent back from the object and enters the eyes. We can see objects only when there is light.

Content - Reflection of Light Formation of image in a plane mirror Section-A - Reflection of Light Formation of image in a plane mirror Section-B Section-C - Periscope, Kaleidoscope Quit Quit

Section-A Reflection of light When light is incident on the surface of an object some of the light is sent back and this phenomenon is called reflection of light. Click on each item to study more. Contents Types Terms Laws

Section-A Reflection Regular Reflection Diffuse Reflection Click on each item to study more.

Section-A Regular Reflection When a parallel beam of light is incident on a plane mirror, the angles of incidence of all the rays are equal. Thus all the rays are reflected in one direction. Such reflection of light is called regular reflection. smooth surfaces

Section-A Diffuse Reflection When a parallel beam of light is incident on a rough surface, the rays are reflected in different directions. Such reflection of light is called diffuse reflection. rough surfaces

N A O B i r Terms on reflection of light normal angle of incidence Section-A Terms on reflection of light normal angle of incidence angle of reflection N A O B i r incident ray reflected ray M M' Click on each item to study more.

Section-A An incident ray AO A ray which represents the incident light is an incident ray. A O M M'

N B A M' M O A reflected ray OB Section-A A reflected ray OB A ray which represents the reflected light is a reflected ray. A O M M' N B

Section-A A normal ON A line perpendicular to the surface at the point of incidence is called a normal. N A O M M'

N A i M' M O An angle of incidence i Section-A An angle of incidence i An angle between the incident ray and the normal is an angle of incidence. A O M M' N i

N B A r i M' M O An angle of reflection r Section-A An angle of reflection r An angle between the reflected ray and the normal is an angle of reflection. N A O M M' i B r

2. The angle of incidence is equal to the angle of reflection. Section-A Laws of Reflection 1. The incident ray, the reflected ray and the normal all lie in the same plane. 2. The angle of incidence is equal to the angle of reflection. Exercise-1

Formation of image in a plane mirror Section-B Formation of image in a plane mirror Stand in front of a looking glass and look at your image. 1. Can you receive your image on a screen ? 2. Is the image erect or inverted? 3. Is the image the same size or larger or smaller? 4. What happens when you tilt your head to the right? 5. How does the image move when you step forward or backward 6. Where is the image formed ?

Formation of image in a plane mirror Section-B Formation of image in a plane mirror The properties of the image formed in a plane mirror are as follows:- The image is virtual. The image is erect. The image is of the same size as the object. The image is laterally inverted. The image is as far behind the mirror as the object is in front. The image is situated on the line passing through the object and perpendicular to the plane mirror. Exercise-2

Section-C Instructions: Divide the class into six groups. Group A, B and C have to make a periscope. Group D, E and F have to make a kaleidoscope. Follow the instructions given in the websites.

Section-C Let’s make a periscope. Click on the "Periscope" to view the web site. Periscope A periscope is an optical instrument that lets you see around corners and over walls. Click here to view the web page and make a periscope.

let’s make a kaleidoscope. Section-C Click on the "Kaleidoscope" to view the web site. let’s make a kaleidoscope. Kaleidoscope A kaleidoscope is a tube containing mirrors and small pieces of coloured paper cut into tiny shapes. It uses reflections to make colourful patterns. Click here to view the web page and make a kaleidoscope.

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Science Group, B.E.H.S (2) Dagon, Union of Myanmar Web References– Credit Created by – Daw Khin Khin Thein and Science Group, B.E.H.S (2) Dagon, Union of Myanmar Web References– http://www.exploratorium.edu/science_explorer/periscope.html http://www.town4kids.com/town4kids/kids/science/explore/kalei.htm Quit