Science STD 6 Chapter 8: Light, Shadows and Reflections - Exercises
1. Rearrange the boxes given below to make a sentence that helps us understand opaque objects.
OWS SHAD AKE OPAQUE O BJEC TSM
Opaque objects make shadows.
2. Classify the objects or materials given below as opaque, transparent or translucent and luminous or non-luminous:
Air, water, a piece of rock, a sheet of aluminium, a mirror, a wooden board, a sheet of polythene, a CD, smoke, a sheet of plane glass, fog, a piece of red hot iron, an umbrella, a lighted fluorescent tube, a wall, a sheet of carbon paper, the flame of a gas burner, a sheet of cardboard, a lighted torch, a sheet of cellophane, a wire mesh, kerosene stove, sun, firefly, moon.
Opaque & Non-Luminous: A piece of rock, a sheet of aluminium, a wooden board, a CD, a wall, a sheet of carbon paper, a sheet of cardboard, an umbrella, a wire mesh.
Transparent & Non-Luminous: Air, water, a sheet of plane glass.
Translucent & Non-Luminous: A sheet of polythene, smoke, fog, a sheet of cellophane.
Luminous: A piece of red hot iron, a lighted fluorescent tube, the flame of a gas burner, a lighted torch, the Sun, a firefly.
Other: A mirror (non-luminous, but reflects light), moon (non-luminous, but reflects sunlight), kerosene stove (non-luminous, but provides light when lit).
3. Can you think of creating a shape that would give a circular shadow if held in one way and a rectangular shadow if held in another way?
Yes, a cylindrical pipe can give a circular shadow when held so that the light source is shining along its length. It will give a rectangular shadow when the light source shines on its side.
4. In a completely dark room, if you hold up a mirror in front of you, will you see a reflection of yourself in the mirror?
No, you will not see a reflection. For a reflection to be visible, light must fall on the object and then be reflected into the mirror. In a completely dark room, there is no light source, so no reflection will be formed.
Suggested Activities
1. Make a row of your friends... A,B,C, or D. If, A is able to see B in the mirror then, can B also see A in the mirror?
Outline: This activity demonstrates the principles of reflection and how light travels in straight lines. When light from person A hits the mirror and reflects to person B's eyes, the reverse path is also true. The answer is yes, if A can see B in the mirror, B can also see A in the mirror. This is because the path of light is reversible.
2. Daayan-Baayan-Take a comb in your right hand... In your mirror reflection... Is it the right hand or the left?
Outline: This activity demonstrates lateral inversion in mirrors. When you hold a comb in your right hand and look in a mirror, the reflection will show the comb in the left hand of your image. This is because a mirror flips objects horizontally, not vertically. The activity helps students understand that reflections are not perfect copies of objects.
3. Magic Device -... a periscope... that uses reflections to see around corners!
Outline: This activity is a hands-on project to build a simple periscope, which uses the principle of reflection to see objects that are not in direct sight. By placing two mirrors at a 45-degree angle inside a "Z" shaped box, light from the object is reflected from the top mirror to the bottom mirror and then to the observer's eye. This demonstrates how reflections can be manipulated for practical uses.