Std : VI

LESSON -11

LIGHT, SHADOWS AND REFLECTIONS

Learning Objectives:  Able to classify objects in terms of transparent, translucent and opaque  Able to identify the characteristics of shadow  Able to analyze rectilinear propagation of light and reflection of light Answer the following: 1. Differentiate between luminous and non-luminous objects. An object that gives out of its own light is called a luminous object. Eg: Sun, stars, firefly An object that does not emit light is called a non-luminous object. Eg: Animals, chairs, Moon 2. What is rectilinear propagation of light? The property of light by which it travels in a straight line is called rectilinear propagation of light. 3. Write an activity to show that light travels in a straight line. Place a lighted candle on a table. Take a rubber tube and look at the flame through the tube. Candle flame can be seen clearly. Bend the tube slightly and try to see the flame. Candle flame cannot be seen through the bent tube. This activity shows that light travels in a straight line. 4. What is a shadow? What conditions are necessary for the formation of a shadow? A shadow is a dark space formed behind an opaque object when it blocks light from any source of light. The conditions necessary for the formation of a shadow are: 1. A source of light. 2. An opaque object to obstruct the path of light. 3. An opaque screen behind the object. 5. List out the characteristics of a shadow. The characteristics of a shadow are as follows: 1. It is always dark, regardless of the colour of the objects or the colour of the light used to make the shadow. 2. It only shows the dark outline of the object and not the details of the object. 3. It is formed in the direction opposite to the side of the source of light. 4. The size of the shadow varies depending on the distance between the object and the screen. 6. Define the following terms: (a) Reflection of light The process of sending back the light rays that fall on the surface of an object is called reflection of light. (b) Lateral inversion

If we stand before a mirror and hold our right ear with our right hand, it appears in the mirror that we are holding left ear with our left hand. This left-right reversal of an ‘object’ and its ‘mirror image’ is called lateral inversion.

7. Differentiate between image and shadow. Points of difference Image 1. Colour The image is of the same colour as the object. 2. Details 3. Lateral inversion 4. Formation

Shadow The shadow is always dark regardless of the colour of the object. The image gives all the details The shadow shows no details of the object. of the object. The image undergoes lateral The shadow does not undergo inversion. lateral inversion. The image is formed when light The shadow is formed when from the object after reflection the path of light is obstructed reaches our eyes. by an opaque object.

ACTIVITIES 1. Make a pinhole camera and explain the principle behind it. 2. Collect pictures showing the phenomenon of lateral inversion and stick it in activity file. New Terms: 1. Luminous objects 2. Translucent 3. Rectilinear propagation 4. Shadow 5. opaque 6. Pinhole camera 7. Bounces 8. Reflection 9. Lateral inversion Prepared By Mrs. Sheeja Shafi [F.N]