NCERT Solutions for Class 6 Science Chapter 11 Light, Shadows and Reflections
NCERT Solutions for Class 6 Science Chapter 11 Light, Shadows and Reflections
These NCERT Solutions for Class 6 Science Chapter 11 Light, Shadows and Reflections Questions and Answers are prepared by our highly skilled subject experts to help students while preparing for their exams.
Light, Shadows and Reflections NCERT Solutions for Class 6 Science Chapter 11
Class 6 Science Chapter 11 Light, Shadows and Reflections Textbook Exercise Questions and Answers
Question 1.
Rearrange the boxes given below to make a sentence that helps us understand opaque objects.
Answer:
Question 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.
Answer:
a. Opaque: A piece of rock, a sheet of aluminium, a minor, a wooden board, a wall, a sheet of cardboard.
b. Transparent: Air, water, a sheet of plain glass.
c. Translucent: A sheet of polythene, a CD, smoke, fog, a sheet of carbon paper, a sheet of cellophane.
d. Luminous objects: A piece of red hot iron, a lighted florescent tube, the flame of a gas burner, a lighted torch, sun, firefly, moon.
e. Non-luminous objects: An umbrella, a wire mesh, kerosene stove.
Question 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?
Answer:
Yes, there are many things which give a circular shadow if held in one way and a rectangular shadow if held in another way. For example, a cylinder, a circular disc, etc.
Question 4.
In a completely dark room, if you hold up a mirror in front of you, will you see a right left inverted image of yourself in the mirror?
Answer:
In a completely dark room, there is no source of light so, we cannot see our right left inverted image and we can see only our image in the mirror, when light is reflected from the mirror.
NCERT Extended Learning Activities And Projects
Question 1.
Make a row of your friends – A, B, C and D, standing in a line. Let one friend stand in front facing them and holding out a mirror towards them (Fig. 11.10 of NCERT).
Now, each person can tell who they are able to see in the Mirror. A, B, C, or D
If, A is able to see B in the mirror then, can B also see A in the mirror? Similarly, for any two pairs amongst A, B, C, or D?
If A is not able to see B in the mirror, then, is B able to see A in the mirror?
Similarly, for any two pairs amongst A, B, C, or D?
This activity tells us something about the way light travels and gets reflected from mirrors. You will learn more about this in higher classes.
Hint:
Do it yourself.
Question 2.
Daavan-Baayan – Take a comb in your right hand and bring it up to your hair and look at yourself in the mirror. There is your familiar face, grinning at you. Wait, try and find out which is the hand holding the comb, in your mirror reflection. Is it the right hand or the left? You were holding it in your right hand, isn’t it?
While a pinhole camera seems to be giving us upside down images, a mirror seems to be turning right hand into left hand and the left into right hand. We will learn more about this in the higher classes.
Hint:
Do it yourself.
Question 3.
Magic Device – In the chapter on symmetry in your Mathematics textbook, you might have made an interesting device kaleidoscope, that uses reflections. Now, let us make another device, a periscope, that uses reflections to see around corners! Ask one of your friends to stand in the corridor just out side the entrance to the classroom with a mirror in hand. Ask another friend also holding a mirror, to stand in the middle of classroom in front of the entrance. Now ask your friends to adjust their mirrors in such a way that the image of object on the other side of the corridor becomes visible to you while you are standing inside the class (Fig. 11.11 of NCERT).
You can make a simple periscope by placing two mirrors in a ‘Z’ shaped box as shown in Fig. 11.12 of NCERT.
Activity 1
Objective: To show that light travels in a straight line path.
Materials Required: A lighted candle and a rubber tube.
Procedure:
- Fix a lighted candle on a table.
- Now, stretch the rubber tube and look through it at the flame of the candle with one eye (keep the other eye closed).
You can see the candle light through it. - Now, bend the rubber tube a little bit and look through it at the candle flame.
- You cannot see the candle flame this time.
Observations: When the rubber tube is straight, candle flame can be seen but when it is bent, the candle flame cannot be seen.
Conclusion: Light travels in a straight line.
- Obstacle: Obstacle is the object which comes in the way of light.
- Luminous objects: Luminous objects are the objects which produce their own light. For example, sun, stars, firefly, etc.
- Non-luminous objects: Non-luminous are the objects which do not produce their own light. For example, table, bag, book, etc.
- Transparent objects: Transparent objects are the objects which allow light to pass through them easily and we can see through them clearly. Example, air, water, etc.
- Translucent objects: Translucent objects are the objects which allow the light pass through them partially and we cannot see clearly through them. Example, wax paper, butter paper, etc.
- Opaque objects: Opaque objects are the objects which do not allow light to pass through them and we cannot see at all through them. Example, wood, stone, etc.
- Shadow: Shadow is the dark patch which is formed on the other side of the objects, i. e., opposite to the light source.
Activity 2
Objective: To show the various shadows of a hand.
Material Required: A torch.
Procedure:
- Light a torch in a dark room.
- Make the light of the torch fall on the wall of the room.
- Now fold your hands in different gestures and between the torch and the wall.
- Observe the wall.
Observations: You will see the different animals shapes on the wall.
Conclusion: Shadows can mislead about the shape of the objects. We have created shadow which do not match with the objects.
Activity 3
Objective: To show the formations of a shadow.
Materials Required: A torch, white cardboard and a ball.
Procedure:
- Light a torch in a dark room.
- Keep the sheet of the white cardboard vertically in front of the torch at some distance.
- Put the ball in front of the torch, close to the cardboard.
Observations: A shadow of the ball is formed on the cardboard screen.
Conclusion: The ball acts as an obstacle in the path of light of the torch. Because of this, rays from the torch light do not go behind the ball. So, the part of the cardboard screen behind the ball does not get any light and remains dark. This dark region on the screen is the shadow of the ball.
- Umbra: Umbra is the darkest part of the shadow which occurs in the centre and where light does not reach.
- Penumbra: Penumbra is the region which surrounds the umbra where some light reaches.
Pinhole Camera: Take two boxes (one large and the other small) so that one of them can slide into the other without any gap in between them. Cut open one side of each box. Make a small hole in the middle on the opposite face of the larger box. Cut out a square shape of about 5 to 6 cm in the middle of the opposite face of the smaller box. Cover this square with a tracing paper Slide the smaller box inside the larger one in such a way that the side with the tracing paper is inside. Your pinhole camera it is ready for use. Hold the pinhole camera and look through the open face of the smaller box. Use a piece of black cloth to cover your head while looking through the pinhole camera. Now look at the object that you want to capture in the camera. Make sure that the object is in bright sunlight. Move the smaller box forward or backward till you get a sharp image on the tracing paper. A pinhole camera forms an inverted image of the object on the screen. It is used to view images of objects, such as buildings and trees and for viewing solar eclipses.
Reflection of light: It is the phenomenon in which a ray of light falls on a smooth polished surface and bounces back in the same medium.
Mirror: Mirror is a smooth, highly polished reflecting surface that reflects the light falling on it. Incident may is the ray that falls on the mirror and reflected ray is the ray which bounces back.
Class 6 Science Chapter 11 Light, Shadows and Reflections Additional Important Questions and Answers
Very Short Answer Type Questions
Question 1.
Name the energy which enables us to see.
Answer:
Light.
Question 2.
Which objects allow the light to pass through them?
Answer:
Transparent.
Question 3.
Whether the moon is a luminous or a non-luminous body?
Answer:
Non-luminous.
Question 4.
What is a shadow?
Answer:
The dark patch formed on the other side of the object, opposite to the light source, is called shadow.
Question 5.
Define umbra.
Answer:
The darker part of the shadow, which always occurs in the centre, is called the umbra.
Question 6.
Define penumbra.
Answer:
The partial dark region which surrounds the umbra is called the penumbra.
Question 7.
What is the principle that a pinhole camera is based on?
Answer:
Light travels in a straight line.
Question 8.
What is reflected ray of light?
Answer:
The ray of light that comes back after suffering reflection from a mirror is called reflected ray of light.
Question 9.
Name one natural source of light.
Answer:
Sun.
Question 10.
What is the essential condition for the formation of shadow?
Answer:
A shadow is formed only when there is a surface/screen behind the opaque object.
Question 11.
Does sun change its position from morning to evening?
Answer:
Yes.
Question 12.
Does the shadow of flying bird reach the earth?
Answer:
No.
Question 13.
What happens when the pinhole of the camera is turned towards a bright object?
Answer:
A real inverted image of the object is formed on the screen.
Question 14.
What is a mirror?
Answer:
A smooth, highly polished reflecting surface is called mirror.
Question 15.
Name a device which can be used to see things on the other side of a high wall.
Answer:
Periscope.
Question 16.
Are the edges of a shadow sharp and distinct?
Answer:
Yes.
Short Answer Type Questions
Question 1.
What is light? What is the main source of light on the earth?
Answer:
Light is a form of energy which enables us to see the objects around us. The main source of light on the earth is the sun.
Question 2.
What is the difference between a luminous and a non-luminous body?
Answer:
Luminous bodies emit light on their own. Example, sun, stars, burning candle etc. Non-luminous bodies do not emit light on their own. Example, moon, earth, blackboard, etc.
Question 3.
What is a pinhole camera? How does it work?
Answer:
The device which forms a photograph like image of a bright object on a screen is called pinhole camera. When the pinhole of the camera is turned towards a bright object a real inverted image of the object is formed on the screen.
Question 4.
Explain the structure of plane mirror.
Answer:
Plane mirror is the most common type of mirror. It is a thin, flat and a smooth sheet of glass having a shiny coating of silver metal on one side. The silver coating is protected by a layer of red paint.
Question 5.
Give two important differences between the pinhole image and the shadows.
Answer:
The important differences between the pinhole images and the shadows are:
- The pinhole image of an object is inverted whereas the shadow of an object is erect.
- The pinhole image of an object is of the same colour as the object but the shadow of an object is always black.
Question 6.
What are the essential conditions for the formation of shadow?
Answer:
The essential conditions for the formation of shadow are:
- There should be an opaque material in the path of light.
- There should be a source of light and screen.
- The object must be placed in the path of light.
Question 7.
Why can we clearly see a burning candle through a sheet of clear glass?
Answer:
If we look at a burning candle through a sheet of clear glass, we can see the candle and its flame clearly. This is because glass is a transparent material which allows all the light coming from the candle and its flame to pass through it.
Question 8.
How will you convert a glass sheet into a translucent sheet?
Answer:
There are following two methods to convert glass sheet into a translucent sheet:
- By smearing a thin layer of oil on the glass sheet.
- By covering a side of sheet by butter paper.
Question 9.
Though we cannot see the sun through clouds on a cloudy day but still there is some sunlight all around. Give reason.
Answer:
This is because being translucent, clouds allow some of the sunlight to pass through them due to which there is light on earth even in a cloudy day.
Long Answer Type Questions
Question 1.
On the basis of the passing of light through the object, what are the different type of objects? Explain them.
Answer:
Transparent objects: The objects which allow the light to pass through them easily and through which we can see clearly are known as transparent objects. Air, water, glass, etc., are transparent objects.
Translucent objects: The objects which allow the light to pass through them partially and we cannot see clearly through them are called translucent objects. Thin paper, oily paper etc., are translucent objects.
Opaque objects: The objects which do not allow the light to pass through them at all are called opaque objects. Walls, books, etc., are opaque objects.
Question 2.
What is a shadow? Write the characteristics of a shadow.
Answer:
The dark patch formed on the other side of objects, opposite to the light source, is called a shadow. The characteristics of a shadow are:
- The shadow of an object is formed on the opposite side of the light source.
- The position of the shadow changes with the position of the light source. This may be seen that as the position of the sun changes from morning to evening, the length and direction of the shadow also changes.
- The position of the shadow changes with the movement of the object.
Question 3.
What are the advantages and disadvantages of a pinhole camera?
Answer:
Advantages:
- In pinhole camera not focusing is required.
- There is no lens in pinhole camera. Therefore, the image is free from spherical and chromatic aberrations.
Disadvantages:
- The image formed does not give any details.
- Image is obtained on the screen so no permanent record of the image can be obtained.
Question 4.
Explain real images and virtual images with examples.
Answer:
The image which can be obtained on a screen is called a real image. In a cinema hall, we see the images of actors on the screen. So, the images formed on a cinema screen are an example of real image. Real images are formed when light rays from an object actually meet at a point after reflection from a mirror.
The image which cannot be obtained on a screen is called a virtual image. A virtual image can be seen only by looking into a mirror. The image of our face formed by a plane mirror cannot be obtained on a screen. It can be seen only- looking into the mirror. So, the image of our face in a plane mirror is an example of a virtual image.
Picture-Based Questions
Question 1.
a. Identify the device shown below.
b. What type of image is formed in in it?
Answer:
a. It is a pinhole camera.
b. Real and inverted imaged.
Question 2.
a. Name the device shown here.
b. Is the image formed here inverted or erect?
c. Give one use of this device.
Answer:
a. Periscope.
b. Erect image.
c. It is used in submarines to see things above water surface.
The Complete Educational Website