Class 6 Science Chapter 11 Important Questions
Class 6 Science Chapter 11 Important Questions of Light, Shadows and Reflections. These extra question answers are helpful in revision of chapter quickly. After doing NCERT Textbook, these important extra questions take very less time to revise the entire chapter for exams.Questions as well as answers are confined to NCERT Books only. These short and long question answers ensure scoring good marks in tests and exams.
Class 6 Science Chapter 11 Important Questions for 2020-2021
|Chapter: 11||Light, Shadows and Reflections|
|Contents:||Important Questions with Answers|
Class 6 Science Chapter 11 Important Extra Questions Set – 1
Write down the different objects we can see around us.
We can see so many objects around us, colorful and different. On the way to school we see things like buses, cars, cycles, trees, animals and sometimes flowers and so many things.
Light helps us see objects. Discuss with an example.
Suppose we go inside a completely dark room. We are not able to see any objects in the room. But when we light a candle or a torch, we can see the objects present in the room. Without light, things cannot be seen. Light helps us see objects.
What do you mean by luminous objects?
An object which gives out its own light is called a luminous object. The sun, stars, lighted electric bulb, lighted torch, burning candle, glowing tube-light, the flame of a gas burner and firefly are all examples of “luminous objects”.
This is because they give out their own light. The luminous objects are in fact the source of light. Since, luminous objects give out their own light they can be seen even in the dark.
A luminous object can be seen because the light given out by it enters our eyes. Comment.
An object which gives out its own light is called a luminous object. As an example, we can see the sun because the light given out by the sun enters our eyes. Similarly, we can see an electric bulb at night (when it is switched on) because light given out by the glowing bulb enters our eyes. Hence, when the light enters our eyes, we can see the objects at night or day time.
What do you mean by “non-luminous” object? Give examples.
An object which does not give out its own light is called a non-luminous object. The table, chair, book, pen, pencil, trees, plants, grass, car, bus, mirror, camera, moon etc., all are examples of non-living objects. This is because they do not give out their own light.
Boojho and Pehli wants to know that how do we see non-luminous objects as they have no own lights? If you know the answer to this question, then tell them.
The non-luminous objects can be seen only when light coming from a luminous object (like the sun, an electric bulb or tube-light or torch, candle etc.) falls on them. This light is reflected by non-luminous object in all directions. When this reflected light enters our eyes, we can see the non-luminous objects.
“Moon gives light to us but it is considered as non-luminous objects”. Justify your answer.
The moon is a non-luminous object which does not have its own light. But the sun is a luminous source of light. Actually, we can see the moon because it reflects sunlight into our eyes. In generally, when sunlight falls on the surface of moon, then some of the sunlight is reflected by the moon towards the earth. And to us it appears as if the light is being given out by the moon itself. But in reality, moonlight is the sunlight which is reflected from the surface of moon. Thus, moon behaves as a cold, non-luminous mirror. It is a reflector of sunlight.
“We can see many things kept in a room during the day on which sunlight does not fall directly”. How, explain.
All the objects outside the room (direct sunlight) scatter the sun light falling on them in all the directions. Even the air scatters some sunlight. It is this scattered sunlight which enters the room and helps us to see the things lying in the room which are not in direct sunlight. In the other words, when the reflected light coming from the table or other object, the light enters our eyes, then we are able to see the table or certain object.
How would you know that any object is transparent?
Those materials which allow all the light to pass through them are called transparent materials. We can see clearly through the transparent materials. The materials like glass, polythene, water, air, groundnut oil are transparent materials. The transparent objects allow all the light to pass through them because they do not absorb or reflect any light. If we are able to see through an object clearly it is allowing all the light to pass through it and hence it is a transparent object.
How would you know that any object is translucent?
Those materials which allow only some of the light to pass through them are called translucent materials. We cannot see clearly through a translucent material. The materials like butter paper, oiled paper, tissue paper, ground glass or frosted glass, sheet of white cotton, muddy water and clouds are transparent materials. The translucent objects absorb or reflect a good part of the light falling on them and allow only some of the light to pass through them.
If we can see through an object but not clearly, it is allowing the light to pass through it only partially and hence it is a translucent object.
What do you mean by opaque materials?
Those materials which do not allow any light to pass through them are called opaque materials. We cannot see anything through an opaque object. The materials like cardboard, door, window, brick, wall, stone, book, wood, metal sheet etc., all are opaque materials. The opaque objects do not allow light to pass through them because they absorb or reflect all the light falling on them.
If we cannot see through an object at all, it is not allowing any light to pass through it and hence it is an opaque object.
What exactly are shadows? Explain.
When an object is placed in front of a source of light, it produces a shade or dark area behind it or opposite side. The “shade” cast by an object is called its “shadow”. Shadows are formed when light is stopped by an object. An opaque object stops the light completely, so and opaque object casts a dark shadow behind it. A translucent object stops the light partially, so a translucent object casts of week shadow or less dark shadow. A transparent object does not stop any light from passing through it, so a transparent object does not cast any shadow behind it.
Write down the different characteristics of shadow which is created by an object.
The shadow of an object has the following characteristics:
i)The shadow of an object is erect that means same side up as the object.
ii)The shadow of an object is real that means it can be formed on a screen.
iii) Irrespective of the colour of the object, the shadow is always black.
iv) The shadow can be smaller than the object, equal to the object or bigger than the object.
What would happen if a flashlight was lit on a person’s face in an open area in the evening? Explain with an activity.
In the evening, go out in an open ground with a few friends. Take a torch and a large sheet of cardboard with you. Hold the torch close to the ground and shine it upwards so that its light falls on your friend’s face. You now have a source of light that is falling on an opaque object. If there were no trees, building or any other object behind your friend. This does not mean that there is no shadow. After all, the light from the torch is not able to pass through his body to the other side. Now, ask another friend to hold the cardboard sheet behind your friend. Thus, the shadow can be seen only on a screen. The ground, walls of a room, a building, or other such surfaces act as a screen for the shadows you observe in everyday life. Shadows give us some information about shapes of objects. Sometimes, shadows can also mislead us about the shape of the object.
“When the bird is flying high up in the air, even then the bird obstructs the sunlight falling on it but its shadows is not seen on the ground”. Explain.
The bird of obstructs the sunlight to form shadow on the nearby ground. But when the same bird is flying high up in the air, even then the bird of obstructs the sunlight falling on it but its shadow is not seen on the ground because the ground is very, very far below the bird.
“The shadow formed by a fluorescent tube light cannot be seen clearly”. Justify your answer.
An electric bulb and the candle form sharp shadows because they are comparatively small source of light. A fluorescent tube light does not form sharp shadows because it is a quite large source of light. Since a fluorescent tube light is very long, therefore some of the light form it always reaches behind the opaque objects leading to the formation of very faint shadows. In fact, the shadows are formed by fluorescent tube lights are so faint that it is usually very difficult to see them.
Describe the construction and function of pinhole camera.
The pinhole camera consists of a closed box having a small pinhole in the front and the translucent screen at the back. The translucent screen at the back side of the pinhole camera boxes made of butter paper (also called in tracing paper). The butter paper acts as a screen to receive the image of the object. The pinhole camera is usually used to view the images of various objects like trees and building etc. The pinhole camera works on the principle that light travels in straight lines to the screen.
What is a natural pinhole camera? Discuss.
There is an interesting pin hole camera in nature. Sometimes, when we pass under a tree covered with large number of leaves, we notice small patches of sun light under it. These circular images are, in fact, pin hole images of the sun. The gaps between the leaves, act as the pin holes. These gaps are all kinds of irregular shapes, but, we can see circular images of the sun.
What do you mean by “Mirrors”? Discuss the types of reflection of light.
In science, an object which reflects light well is called a mirror. A plane mirror is a thin, flat and smooth sheet of glass having a shiny coating of silver metal or aluminum metal on one side. The silver coating is protected by a layer of red paint. Remember, the reflection of light in a plane mirror takes place at the silvered surface inside it. A mirror works because it reflects light. A mirror reflects most of the light falling on it in a definite direction.
Explain “real images” and “virtual images”.
The image which can be obtained on a screen is called a real image. The image formed on a cinema screen is an example of real images. A real image is formed when light rays coming from an object actually meet at a point after reflection from the mirror. A real image can be formed on a screen because light rays actually pass through it.
Write down the characteristics of image formed by a plane mirror and its uses.
There are different characteristics of image formed by a plane mirror:
i)The image in a plane mirror is erect.
ii)The image in a plane mirror is of the same image as the object that means that image is neither enlarge not diminished.
iii)The image in a plane mirror is laterally inverted or sideways reversed with respect to the object.
iv)The image formed in a plane mirror is at the same distance behind the mirror as the object is in front of it.
v)The image formed in a plane mirror is virtual or unreal that means it cannot be obtained on a screen.
There are different use of plane mirrors:
i)Plane mirrors are fixed on the walls of certain shops, like jewellery shops, shopping malls etc.
ii)Plane mirror used at home to view our-selves.
iii)Plane mirror used in making periscope.
A student covered a torch with red cello-phones sheet to obtain red light. Using the red light, she obtains a shadow of an Opaque object. She repeats this activity with green and blue lights. Will the colour of the light affect the shadow? Explain.
Shadow is just an absence of light at that place. Shadow is not affected by the colours of the object because the amount of light preventing to pass will remain same.
The shadow is affected by the shape of the object only. If the object is large, the shadow will be large and vice-versa.
Is air around us always transparent? Discuss.
We can see the objects through air clearly, means we can observe all the objects in their original shapes and sizes without any disturbance, it means the environment around us which is just air, must be transparent. But when thick smoke, thick clouds etc. are presents in the air, it does not remain transparent.
What is Shadow? How is it formed? How does the colour of an opaque object, affect the colour of the shadow?
A shadow is a dark outline or image caused by an opaque object that blocks light coming from a source of light. It is formed when light hits the opaque object which does not let the light pass through. Everywhere else around the Opaque object, the light continues in a straight path until it bounces off the ground or wall behind the object. The wall or ground behind the opaque object is the screen. On this screen is a dark patch or shadow with the same outline, as the object surrounded by light.
The colour of the opaque object does not affect the colour of the shadow that is formed.
A football match is being played at night in a stadium with flood lights ON. You can see the shadow of a football kept at the ground but cannot see its shadow when it is kicked high in the air. Explain.
The shadow of an object cannot be caught if the screen and the object are very far from the each other. This is the same case. Here, also the shadow of the football cannot be seen on the ground (which acts as a screen) when it is kicked high in the air. This happens because if we take the object away from the screen, the shadow becomes smaller and smaller in size and a time comes when it totally disappears from the screen.