Class-6 Science, Chapter-11 Light, Shadows and Reflections, Additional exercises with solutions in line with NCERT book / CBSE Syllabus

Chapter 11
Light, Shadows and Reflections 

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Exercises from textbook

Additional Exercises

Tables from Textbook

Activities/Projects

Additional Exercises

Choose the correct answer:

1-    ______is the natural source of light-

a.    Sun (√)

b.    Candle

c.     Lantern

2-    we can see pinhole images of the____ under a tree.

a.    Sun (√)

b.    Clouds

c.     Mountains

3-    We see ­­_______ images of people with our pinhole camera.

a.    Upside down (√)

b.    Upright

c.     None of these

4-    Oily paper is a _______material

a.    Transparent

b.    Translucent (√)

c.     Opaque

5-    Which of the following is not a luminous object?

a.    Sun

b.    Moon (√)

c.     Pole star

Science Class-7

Match the column

Coulmn 1	Column 2
Luminous	Roughened glass
Non-luminous	Wood
Transparent	Sun
Opaque	Air
Translucent	Moon

Answer-

Column 1	Column 2
Luminous	Sun
Non luminous	Moon
Transparent	Air
Opaque	Wood
Translucent	Roughened glass

State whether the following statements are true or false:

1-    In the absence of light w fail to see the surrounding objects.                           (True)

2-    Light is a kind of energy.                                                                                         (True)

3-    It is only due to existence of light that we are able to view the natural beauty.                                                                                                                           (True)

4-    Shadows look different in colour when the colours of objects are different. (False)

5-    Sometimes shadows can mislead us about the shape of the object.           (True)

6-    Images are same as Shadows.                                                                    (False)

7-    Mirror reflection gives us clear images.                                                        (True)

8-    Light travels in a straight line.                                                                       (True)

9-    You see a refraction of your face in the mirror.                                            (False)

Encircle the odd one:

1-    Wood, iron, paper, roughened glass                   (Opaque objects)

2-    Star, sun, moon, firefly                                        (Luminous objects)

3-    Lantern, lightening, torch, bulb                            (Man-made sources of light)

4-    Air, Water, tracing paper, glass                           (Translucent objects)

Fill in the blanks

Transparent material does not obstruct the passage of light.

1.    Opaque materials block the passage of light.

2.    Translucent objects partially allow the light rays to pass through them and a faint shadow is formed on the screen.

3.    Shadow is formed when light passage is blocked by an Opaque object.

4.    Light always travels in a straight line.

5.    Mirror changes the direction of light that falls on it. 

Answer the following questions:

Q. Name some artificial sources of light.
Ans- Following are some artificial sources of light:
Candles
Torch
Lantern
Electric bulb
CFL

Q. Name some natural sources of light.
Ans- Following Are some Natural sources of light
Stars
Sun
Firefly (jugnu)
Lightning caused in clouds during rainy season

Q. Sun is Luminous but moon is non-luminous. Why?
Ans- A luminous object emits its own light. Sun emits its own light while moon reflects the light of sun. Therefore moon is a non luminous object.
Q. When do we see an object?
Ans- Light rays from the sun fall on an object they get reflected from the object and enter into our eyes only then we are able to see the object.
Q. What is the reason for formation of shadow?

               or
How is Shadow formed?Ans- When an Opaque object obstructs the path of light, shadow is formed.

Q. Prove with the help of an experiment that light travels in a straight line.
Ans-

We will light a candle and fix it on a table. Standing at the other end of the room, let us look at the candle through a rubber tube holding it straight. We are able to see the candle.
we will turn the pipe a little to our right or left. Now we are not able to see the candle.
This activities suggest that light travels along a straight line.

Q. Define transparent translucent and Opaque materials.
Ans- Transparent materials - The materials that allow light to pass through them are called as transparent materials. For example water, glass, air

Translucent materials - Translucent materials let some light to pass through them but they scatter the light in all directions. So we cannot see clearly through them. For example - tissue paper, oily paper, roughened glass

Opaque materials- The materials which do not let any light pass through them are opaque materials. For example stone, wood, iron

Exercises from Textbook

Rearrange the boxes given below to make a sentence that helps us understand Opaque objects.

OWS

AKE

OPAQ

UEO

BJEC

TSM

SHAD

Ans-

OPAQ

UE        O

BJEC

TS         M

AKE

SHAD

OWS

(OPAQUE OBJECTS MAKE SHADOWS)

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

Object	Opaque/ Transparent / Translucent	Luminous / Non luminous
Air	Transparent	Non luminous
Water	Transparent	Non luminous
A piece of rock	Opaque	Non luminous
A sheet of aluminium	Opaque	Non luminous
A mirror	Opaque	Non luminous
A wooden board	Opaque	Non luminous
A sheet of polythene	Transparent	Non luminous
A CD	Opaque	Non luminous
Smoke	Translucent	Non luminous
A sheet of plane glass	Transparent	Non luminous
Fog	Translucent	Non luminous
A piece of red hot iron	Opaque	Luminous
An umbrella	Opaque	Non luminous
A lighted fluorescent tube	Opaque	Luminous
A wall	Opaque	Non luminous
A sheet of carbon paper	Opaque	Non luminous
The flame of a gas burner	Opaque	Luminous
A sheet of cardboard	Opaque	Non luminous
A lighted torch	Opaque	Non luminous
A sheet of cellophane	Transparent	Non luminous
A wire mesh	Translucent	Non luminous
Kerosene Stove (lighted)	Opaque	Luminous
Sun	Opaque	Luminous
Firefly	Opaque	Luminous
Moon	Opaque	Non luminous

Can you think of creating a shape that would give a circular shadow held in one way and a rectangular shadow is held in another way?

Ans-

An opaque cylinder makes rectangular shadow when kept vertically in front of light source.

It makes circular shadow, when kept horizontally in front of light source.

In a completely dark room, hold up a mirror in front of you, will you see a reflection of yourself in the mirror?

In a completely dark room, we can not see a reflection of ourselves in the mirror as there is no light and the mirror forms image by the reflection of light.

Tables from Textbook

Table 11.1

Object / Material	View through the object possible (fully / partially / not at all)	Object is opaque / transparent / translucent
Pencil	Not at all	Opaque
Rubber ball	Not at all	Opaque
Sheet of writing paper	Not at all	Opaque
Tracing Paper	Partially	Translucent
A piece of cloth	Not at all	Opaque
Chiffon dupatta	Partially	Translucent
Vinyl sheet	Not at all	Opaque
Water in a bucket	Fully	Transparent
Eye glasses	Fully	Transparent
Colourless Polyethen sheet	Fully	Transparent
Wooden door	Not at all	Opaque
Butter paper	Partially	Translucent

Activity / Project

Suggested activities
(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.

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, can B also to see A in the mirror? Similarly, for any two pairs amongst A, B, C or D

This activity tell us something about the way light travels and gets reflected from Mirrors. 

(2) Daayan-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 family face, grinning at you.☺

Wait, try to 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. 

(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 corridor just outside 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 other side of the corridor becomes visible to you while you are standing inside the class.

You can make a simple Periscope by placing two Mirrors in a z shaped box in the following figure.

Things to think about
Opaque objects cast Shadows, isn't it? Now, if we hold a transparent object in the sun, do we see anything on the ground that gives us a hint that we are holding something in our hand?

We saw that changing colour of opaque objects does not change the colour of their Shadows. What happens if we place an Opaque object in coloured light? You can cover the face of a Torch with coloured transparent paper to do this.(Did you ever noticed the colours of evening shadows just as the sun is setting?)

Things to read
Rudyard Kipling's " just so stories" particular, the story of "How the Leopard got its spots"  where he mentions stripy, speckly, patchy-blatchy shadows. Here are a few lines from this story, that has a lot of shadows 

.....after ever so many days, they saw a great, high, tall forest full of tree trunks all ‘sclusively speckled and sprottled and spottled, dotted and splashed and slashed and hatched and cross-hatched with shadows. (Say that quickly aloud, and you will see how very shadowy the forest must have been.)

'What is this,' set the Leopard,' that is so 'sclusively dark, and yet so full of little pieces of light?’

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