Class 7 Science Chapter 11 NCERT Book - Light: Shadows and Reflections

 Page 1


Light: Shadows and 
Re? ections 
11
In the Western Ghat region of Maharashtra, Keshav spends 
part of his summer vacation at his friend Jatin’s grandparents’ 
village. Having lived in a big city, he ? nds the forests, fresh 
air, sounds of gushing streams, and chirping birds a novel 
experience.
However, for Keshav, the most fascinating sight is the 
dance of hundreds of ? re? ies at night, ? ashing their lights 
in a wonderful performance. Jatin’s grandparents explain 
that ? re? ies are seasonal insects and they use light to 
communicate. Unfortunately, Keshav also learns the number 
of ? re? ies is decreasing due to light pollution, reduced forest 
cover, and excessive tourism.
At the end of their vacation, Keshav and Jatin board an 
evening bus back to their city. As the bus winds through the 
hilly roads, Keshav watches the moonlit landscape and the 
beams from the headlights of passing vehicles ? ashing by. He 
is reminded of the many poems and songs about moonlight, 
and wonders — does the Moon actually produce its own 
light? Did we not learn in the chapter ‘Beyond Earth’ in the 
Grade 6 Science textbook Curiosity that all other objects in 
our solar system shine only by re? ecting the light of the 
Sun? Is moonlight just re? ected sunlight? Which objects give 
o?  their own light? While thinking, he notices something 
strange — light seems to move in a straight line!
Chapter 11.indd   153 4/3/2025   4:56:22 PM
Page 2


Light: Shadows and 
Re? ections 
11
In the Western Ghat region of Maharashtra, Keshav spends 
part of his summer vacation at his friend Jatin’s grandparents’ 
village. Having lived in a big city, he ? nds the forests, fresh 
air, sounds of gushing streams, and chirping birds a novel 
experience.
However, for Keshav, the most fascinating sight is the 
dance of hundreds of ? re? ies at night, ? ashing their lights 
in a wonderful performance. Jatin’s grandparents explain 
that ? re? ies are seasonal insects and they use light to 
communicate. Unfortunately, Keshav also learns the number 
of ? re? ies is decreasing due to light pollution, reduced forest 
cover, and excessive tourism.
At the end of their vacation, Keshav and Jatin board an 
evening bus back to their city. As the bus winds through the 
hilly roads, Keshav watches the moonlit landscape and the 
beams from the headlights of passing vehicles ? ashing by. He 
is reminded of the many poems and songs about moonlight, 
and wonders — does the Moon actually produce its own 
light? Did we not learn in the chapter ‘Beyond Earth’ in the 
Grade 6 Science textbook Curiosity that all other objects in 
our solar system shine only by re? ecting the light of the 
Sun? Is moonlight just re? ected sunlight? Which objects give 
o?  their own light? While thinking, he notices something 
strange — light seems to move in a straight line!
Chapter 11.indd   153 4/3/2025   4:56:22 PM
Curiosity | Textbook of Science | Grade 7
154
11.1 Sources of Light 11.1 Sources of Light 11.1 Sources of Light 11.1 Sources of Light 11.1 Sources of Light 11.1 Sources of Light 11.1 Sources of Light 11.1 Sources of Light
The Sun gives out or emits its own light and is the main source 
of natural light on the Earth. Stars, lightning, natural ? re, and 
certain animals also emit their own light (Fig. 11.1).
In ancient times, humans learnt to create 
? re — the earliest form of arti? cial lighting. With 
time, they learnt to create 
? re using di? erent fuels, 
such as animal fat, oil, 
wax, and gas (Fig. 11.2). 
With the invention of 
electricity and di? erent 
kinds of electric light 
sources, most of the 
lighting needs of humans 
are now met by electric 
lighting (Fig. 11.3).
Objects that emit their own light are 
called luminous objects. Objects that 
do not emit their own light are called 
non-luminous objects. The Moon is a 
non-luminous object. It does not emit its 
own light. It just re? ects the light emitted 
by the Sun that falls on it.
SCIENCE AND SOCIETY
Light Emitting Diode (LED) lamps are modern light 
sources that consume much less power, are brighter 
and last longer than traditional lamps. This not 
only reduces electricity bills but is also better for 
environment. Recognising their advantages, the 
Indian government has made substantial e? orts to 
promote the use of LED lamps nationwide. At their 
end of life, LED lamps must be appropriately disposed 
or recycled, and not thrown in the garbage.
and last longer than traditional lamps. This not 
only reduces electricity bills but is also better for 
environment. Recognising their advantages, the 
Indian government has made substantial e? orts to 
promote the use of LED lamps nationwide. At their 
end of life, LED lamps must be appropriately disposed 
or recycled, and not thrown in the garbage.
Fig. 11.3: Some sources of electric light
 objects. The Moon is a 
non-luminous object. It does not emit its 
own light. It just re? ects the light emitted 
by the Sun that falls on it.
Fig. 11.3: Some sources of electric light Fig. 11.3: Some sources of electric light
Fig. 11.1: Some natural sources of light
Fig. 11.2: Fire as a source 
of arti? cial light
Chapter 11.indd   154 4/3/2025   4:56:26 PM
Page 3


Light: Shadows and 
Re? ections 
11
In the Western Ghat region of Maharashtra, Keshav spends 
part of his summer vacation at his friend Jatin’s grandparents’ 
village. Having lived in a big city, he ? nds the forests, fresh 
air, sounds of gushing streams, and chirping birds a novel 
experience.
However, for Keshav, the most fascinating sight is the 
dance of hundreds of ? re? ies at night, ? ashing their lights 
in a wonderful performance. Jatin’s grandparents explain 
that ? re? ies are seasonal insects and they use light to 
communicate. Unfortunately, Keshav also learns the number 
of ? re? ies is decreasing due to light pollution, reduced forest 
cover, and excessive tourism.
At the end of their vacation, Keshav and Jatin board an 
evening bus back to their city. As the bus winds through the 
hilly roads, Keshav watches the moonlit landscape and the 
beams from the headlights of passing vehicles ? ashing by. He 
is reminded of the many poems and songs about moonlight, 
and wonders — does the Moon actually produce its own 
light? Did we not learn in the chapter ‘Beyond Earth’ in the 
Grade 6 Science textbook Curiosity that all other objects in 
our solar system shine only by re? ecting the light of the 
Sun? Is moonlight just re? ected sunlight? Which objects give 
o?  their own light? While thinking, he notices something 
strange — light seems to move in a straight line!
Chapter 11.indd   153 4/3/2025   4:56:22 PM
Curiosity | Textbook of Science | Grade 7
154
11.1 Sources of Light 11.1 Sources of Light 11.1 Sources of Light 11.1 Sources of Light 11.1 Sources of Light 11.1 Sources of Light 11.1 Sources of Light 11.1 Sources of Light
The Sun gives out or emits its own light and is the main source 
of natural light on the Earth. Stars, lightning, natural ? re, and 
certain animals also emit their own light (Fig. 11.1).
In ancient times, humans learnt to create 
? re — the earliest form of arti? cial lighting. With 
time, they learnt to create 
? re using di? erent fuels, 
such as animal fat, oil, 
wax, and gas (Fig. 11.2). 
With the invention of 
electricity and di? erent 
kinds of electric light 
sources, most of the 
lighting needs of humans 
are now met by electric 
lighting (Fig. 11.3).
Objects that emit their own light are 
called luminous objects. Objects that 
do not emit their own light are called 
non-luminous objects. The Moon is a 
non-luminous object. It does not emit its 
own light. It just re? ects the light emitted 
by the Sun that falls on it.
SCIENCE AND SOCIETY
Light Emitting Diode (LED) lamps are modern light 
sources that consume much less power, are brighter 
and last longer than traditional lamps. This not 
only reduces electricity bills but is also better for 
environment. Recognising their advantages, the 
Indian government has made substantial e? orts to 
promote the use of LED lamps nationwide. At their 
end of life, LED lamps must be appropriately disposed 
or recycled, and not thrown in the garbage.
and last longer than traditional lamps. This not 
only reduces electricity bills but is also better for 
environment. Recognising their advantages, the 
Indian government has made substantial e? orts to 
promote the use of LED lamps nationwide. At their 
end of life, LED lamps must be appropriately disposed 
or recycled, and not thrown in the garbage.
Fig. 11.3: Some sources of electric light
 objects. The Moon is a 
non-luminous object. It does not emit its 
own light. It just re? ects the light emitted 
by the Sun that falls on it.
Fig. 11.3: Some sources of electric light Fig. 11.3: Some sources of electric light
Fig. 11.1: Some natural sources of light
Fig. 11.2: Fire as a source 
of arti? cial light
Chapter 11.indd   154 4/3/2025   4:56:26 PM
Light: Shadows and Re? ections 
155
11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line?
Let us do an activity to try to ? nd out.
Activity 11.1: Let us investigate
? Take three matchboxes and make a hole in 
the inner tray of each matchbox, exactly at the 
same position.
? Arrange these three matchboxes in a straight 
line. Make sure that all three holes are exactly 
at the same height and are in a line as shown 
in Fig. 11.4.
? Place a torch light on one side of the matchboxes, ensuring 
that its lamp is at the height of the holes.
? Place a cardboard (screen) on the other side of the matchboxes 
and obtain a bright spot on it. (You may need to slightly adjust 
the heights of boxes.)
? Move one of the matchboxes slightly to a side or up and down. 
Are you able to obtain the light spot on the screen now?
When all the three holes are not in the same line, we could not 
obtain the light spot on the screen. These observations suggest 
that light travels in a straight line.
Can we somehow 
check it in some 
other way?
I have an idea. Let us try 
to see the candle ? ame 
through a bent pipe! 
Should we also try out this idea? 
Activity 11.2: Let us explore
Caution — Use a lighted candle under adult supervision 
only.
? Take a long hollow pipe of some ? exible 
material and align it so that you can see the 
candle ? ame as shown in Fig. 11.5a.
? Now, bend the pipe and try to see the candle 
? ame again (Fig. 11.5b). Can you still see it? 
You could see the candle ? ame through a straight 
pipe but not through a bent pipe. This shows that 
light travels in a straight line.
Fig. 11.4: Matchbox activity—
light through holes
Hole
Screen
(a)
(b)
Fig. 11.5: Viewing candle ? ame through 
(a) a straight pipe (b) a bent pipe
Chapter 11.indd   155 4/3/2025   4:56:28 PM
Page 4


Light: Shadows and 
Re? ections 
11
In the Western Ghat region of Maharashtra, Keshav spends 
part of his summer vacation at his friend Jatin’s grandparents’ 
village. Having lived in a big city, he ? nds the forests, fresh 
air, sounds of gushing streams, and chirping birds a novel 
experience.
However, for Keshav, the most fascinating sight is the 
dance of hundreds of ? re? ies at night, ? ashing their lights 
in a wonderful performance. Jatin’s grandparents explain 
that ? re? ies are seasonal insects and they use light to 
communicate. Unfortunately, Keshav also learns the number 
of ? re? ies is decreasing due to light pollution, reduced forest 
cover, and excessive tourism.
At the end of their vacation, Keshav and Jatin board an 
evening bus back to their city. As the bus winds through the 
hilly roads, Keshav watches the moonlit landscape and the 
beams from the headlights of passing vehicles ? ashing by. He 
is reminded of the many poems and songs about moonlight, 
and wonders — does the Moon actually produce its own 
light? Did we not learn in the chapter ‘Beyond Earth’ in the 
Grade 6 Science textbook Curiosity that all other objects in 
our solar system shine only by re? ecting the light of the 
Sun? Is moonlight just re? ected sunlight? Which objects give 
o?  their own light? While thinking, he notices something 
strange — light seems to move in a straight line!
Chapter 11.indd   153 4/3/2025   4:56:22 PM
Curiosity | Textbook of Science | Grade 7
154
11.1 Sources of Light 11.1 Sources of Light 11.1 Sources of Light 11.1 Sources of Light 11.1 Sources of Light 11.1 Sources of Light 11.1 Sources of Light 11.1 Sources of Light
The Sun gives out or emits its own light and is the main source 
of natural light on the Earth. Stars, lightning, natural ? re, and 
certain animals also emit their own light (Fig. 11.1).
In ancient times, humans learnt to create 
? re — the earliest form of arti? cial lighting. With 
time, they learnt to create 
? re using di? erent fuels, 
such as animal fat, oil, 
wax, and gas (Fig. 11.2). 
With the invention of 
electricity and di? erent 
kinds of electric light 
sources, most of the 
lighting needs of humans 
are now met by electric 
lighting (Fig. 11.3).
Objects that emit their own light are 
called luminous objects. Objects that 
do not emit their own light are called 
non-luminous objects. The Moon is a 
non-luminous object. It does not emit its 
own light. It just re? ects the light emitted 
by the Sun that falls on it.
SCIENCE AND SOCIETY
Light Emitting Diode (LED) lamps are modern light 
sources that consume much less power, are brighter 
and last longer than traditional lamps. This not 
only reduces electricity bills but is also better for 
environment. Recognising their advantages, the 
Indian government has made substantial e? orts to 
promote the use of LED lamps nationwide. At their 
end of life, LED lamps must be appropriately disposed 
or recycled, and not thrown in the garbage.
and last longer than traditional lamps. This not 
only reduces electricity bills but is also better for 
environment. Recognising their advantages, the 
Indian government has made substantial e? orts to 
promote the use of LED lamps nationwide. At their 
end of life, LED lamps must be appropriately disposed 
or recycled, and not thrown in the garbage.
Fig. 11.3: Some sources of electric light
 objects. The Moon is a 
non-luminous object. It does not emit its 
own light. It just re? ects the light emitted 
by the Sun that falls on it.
Fig. 11.3: Some sources of electric light Fig. 11.3: Some sources of electric light
Fig. 11.1: Some natural sources of light
Fig. 11.2: Fire as a source 
of arti? cial light
Chapter 11.indd   154 4/3/2025   4:56:26 PM
Light: Shadows and Re? ections 
155
11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line?
Let us do an activity to try to ? nd out.
Activity 11.1: Let us investigate
? Take three matchboxes and make a hole in 
the inner tray of each matchbox, exactly at the 
same position.
? Arrange these three matchboxes in a straight 
line. Make sure that all three holes are exactly 
at the same height and are in a line as shown 
in Fig. 11.4.
? Place a torch light on one side of the matchboxes, ensuring 
that its lamp is at the height of the holes.
? Place a cardboard (screen) on the other side of the matchboxes 
and obtain a bright spot on it. (You may need to slightly adjust 
the heights of boxes.)
? Move one of the matchboxes slightly to a side or up and down. 
Are you able to obtain the light spot on the screen now?
When all the three holes are not in the same line, we could not 
obtain the light spot on the screen. These observations suggest 
that light travels in a straight line.
Can we somehow 
check it in some 
other way?
I have an idea. Let us try 
to see the candle ? ame 
through a bent pipe! 
Should we also try out this idea? 
Activity 11.2: Let us explore
Caution — Use a lighted candle under adult supervision 
only.
? Take a long hollow pipe of some ? exible 
material and align it so that you can see the 
candle ? ame as shown in Fig. 11.5a.
? Now, bend the pipe and try to see the candle 
? ame again (Fig. 11.5b). Can you still see it? 
You could see the candle ? ame through a straight 
pipe but not through a bent pipe. This shows that 
light travels in a straight line.
Fig. 11.4: Matchbox activity—
light through holes
Hole
Screen
(a)
(b)
Fig. 11.5: Viewing candle ? ame through 
(a) a straight pipe (b) a bent pipe
Chapter 11.indd   155 4/3/2025   4:56:28 PM
Curiosity | Textbook of Science | Grade 7
156
11.3  Light through Transparent, 
Translucent, and Opaque Materials Translucent, and Opaque Materials Translucent, and Opaque Materials Translucent, and Opaque Materials Translucent, and Opaque Materials Translucent, and Opaque Materials Translucent, and Opaque Materials Translucent, and Opaque Materials Translucent, and Opaque Materials Translucent, and Opaque Materials Translucent, and Opaque Materials Translucent, and Opaque Materials Translucent, and Opaque Materials Translucent, and Opaque Materials Translucent, and Opaque Materials Translucent, and Opaque Materials
Let us place objects made of 
di? erent materials in the path of 
light and ? nd out.
Activity 11.3: Let us experiment
? Collect objects made of di? erent materials. Also, you will 
need a torch.
Tracing paper
Table 11.1: Light through di? erent materials
Light will pass 
fully/partially/not at all
Cardboard
Paper
Glass
Material
Transparent/ 
Translucent/ 
Opaque
My prediction My observation
Thick cloth
...
...
What happens when an object 
comes in the path of light?
Caution — Use a laser only under teachers’ supervision. Avoid 
using high-power lasers for this activity; a low-power laser 
pointer is su?  cient. Never point the laser beam directly at 
anyone’s eyes, as it can cause serious eye damage.
Pass a laser beam 
through a beaker ? lled with 
water in which a drop of 
milk is added to make the 
laser beam easily visible. 
What do you observe? Do you see that the 
beam of laser light inside water follows a 
straight path? 
However, light can sometimes even bend 
around corners! This is something you will 
learn in the higher grades.
— Use a laser only under teachers’ supervision. Avoid 
using high-power lasers for this activity; a low-power laser 
pointer is su?  cient. Never point the laser beam directly at 
D
IVE
EEPER
Chapter 11.indd   156 4/3/2025   4:56:30 PM
Page 5


Light: Shadows and 
Re? ections 
11
In the Western Ghat region of Maharashtra, Keshav spends 
part of his summer vacation at his friend Jatin’s grandparents’ 
village. Having lived in a big city, he ? nds the forests, fresh 
air, sounds of gushing streams, and chirping birds a novel 
experience.
However, for Keshav, the most fascinating sight is the 
dance of hundreds of ? re? ies at night, ? ashing their lights 
in a wonderful performance. Jatin’s grandparents explain 
that ? re? ies are seasonal insects and they use light to 
communicate. Unfortunately, Keshav also learns the number 
of ? re? ies is decreasing due to light pollution, reduced forest 
cover, and excessive tourism.
At the end of their vacation, Keshav and Jatin board an 
evening bus back to their city. As the bus winds through the 
hilly roads, Keshav watches the moonlit landscape and the 
beams from the headlights of passing vehicles ? ashing by. He 
is reminded of the many poems and songs about moonlight, 
and wonders — does the Moon actually produce its own 
light? Did we not learn in the chapter ‘Beyond Earth’ in the 
Grade 6 Science textbook Curiosity that all other objects in 
our solar system shine only by re? ecting the light of the 
Sun? Is moonlight just re? ected sunlight? Which objects give 
o?  their own light? While thinking, he notices something 
strange — light seems to move in a straight line!
Chapter 11.indd   153 4/3/2025   4:56:22 PM
Curiosity | Textbook of Science | Grade 7
154
11.1 Sources of Light 11.1 Sources of Light 11.1 Sources of Light 11.1 Sources of Light 11.1 Sources of Light 11.1 Sources of Light 11.1 Sources of Light 11.1 Sources of Light
The Sun gives out or emits its own light and is the main source 
of natural light on the Earth. Stars, lightning, natural ? re, and 
certain animals also emit their own light (Fig. 11.1).
In ancient times, humans learnt to create 
? re — the earliest form of arti? cial lighting. With 
time, they learnt to create 
? re using di? erent fuels, 
such as animal fat, oil, 
wax, and gas (Fig. 11.2). 
With the invention of 
electricity and di? erent 
kinds of electric light 
sources, most of the 
lighting needs of humans 
are now met by electric 
lighting (Fig. 11.3).
Objects that emit their own light are 
called luminous objects. Objects that 
do not emit their own light are called 
non-luminous objects. The Moon is a 
non-luminous object. It does not emit its 
own light. It just re? ects the light emitted 
by the Sun that falls on it.
SCIENCE AND SOCIETY
Light Emitting Diode (LED) lamps are modern light 
sources that consume much less power, are brighter 
and last longer than traditional lamps. This not 
only reduces electricity bills but is also better for 
environment. Recognising their advantages, the 
Indian government has made substantial e? orts to 
promote the use of LED lamps nationwide. At their 
end of life, LED lamps must be appropriately disposed 
or recycled, and not thrown in the garbage.
and last longer than traditional lamps. This not 
only reduces electricity bills but is also better for 
environment. Recognising their advantages, the 
Indian government has made substantial e? orts to 
promote the use of LED lamps nationwide. At their 
end of life, LED lamps must be appropriately disposed 
or recycled, and not thrown in the garbage.
Fig. 11.3: Some sources of electric light
 objects. The Moon is a 
non-luminous object. It does not emit its 
own light. It just re? ects the light emitted 
by the Sun that falls on it.
Fig. 11.3: Some sources of electric light Fig. 11.3: Some sources of electric light
Fig. 11.1: Some natural sources of light
Fig. 11.2: Fire as a source 
of arti? cial light
Chapter 11.indd   154 4/3/2025   4:56:26 PM
Light: Shadows and Re? ections 
155
11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line? 11.2 Does Light Travel in a Straight Line?
Let us do an activity to try to ? nd out.
Activity 11.1: Let us investigate
? Take three matchboxes and make a hole in 
the inner tray of each matchbox, exactly at the 
same position.
? Arrange these three matchboxes in a straight 
line. Make sure that all three holes are exactly 
at the same height and are in a line as shown 
in Fig. 11.4.
? Place a torch light on one side of the matchboxes, ensuring 
that its lamp is at the height of the holes.
? Place a cardboard (screen) on the other side of the matchboxes 
and obtain a bright spot on it. (You may need to slightly adjust 
the heights of boxes.)
? Move one of the matchboxes slightly to a side or up and down. 
Are you able to obtain the light spot on the screen now?
When all the three holes are not in the same line, we could not 
obtain the light spot on the screen. These observations suggest 
that light travels in a straight line.
Can we somehow 
check it in some 
other way?
I have an idea. Let us try 
to see the candle ? ame 
through a bent pipe! 
Should we also try out this idea? 
Activity 11.2: Let us explore
Caution — Use a lighted candle under adult supervision 
only.
? Take a long hollow pipe of some ? exible 
material and align it so that you can see the 
candle ? ame as shown in Fig. 11.5a.
? Now, bend the pipe and try to see the candle 
? ame again (Fig. 11.5b). Can you still see it? 
You could see the candle ? ame through a straight 
pipe but not through a bent pipe. This shows that 
light travels in a straight line.
Fig. 11.4: Matchbox activity—
light through holes
Hole
Screen
(a)
(b)
Fig. 11.5: Viewing candle ? ame through 
(a) a straight pipe (b) a bent pipe
Chapter 11.indd   155 4/3/2025   4:56:28 PM
Curiosity | Textbook of Science | Grade 7
156
11.3  Light through Transparent, 
Translucent, and Opaque Materials Translucent, and Opaque Materials Translucent, and Opaque Materials Translucent, and Opaque Materials Translucent, and Opaque Materials Translucent, and Opaque Materials Translucent, and Opaque Materials Translucent, and Opaque Materials Translucent, and Opaque Materials Translucent, and Opaque Materials Translucent, and Opaque Materials Translucent, and Opaque Materials Translucent, and Opaque Materials Translucent, and Opaque Materials Translucent, and Opaque Materials Translucent, and Opaque Materials
Let us place objects made of 
di? erent materials in the path of 
light and ? nd out.
Activity 11.3: Let us experiment
? Collect objects made of di? erent materials. Also, you will 
need a torch.
Tracing paper
Table 11.1: Light through di? erent materials
Light will pass 
fully/partially/not at all
Cardboard
Paper
Glass
Material
Transparent/ 
Translucent/ 
Opaque
My prediction My observation
Thick cloth
...
...
What happens when an object 
comes in the path of light?
Caution — Use a laser only under teachers’ supervision. Avoid 
using high-power lasers for this activity; a low-power laser 
pointer is su?  cient. Never point the laser beam directly at 
anyone’s eyes, as it can cause serious eye damage.
Pass a laser beam 
through a beaker ? lled with 
water in which a drop of 
milk is added to make the 
laser beam easily visible. 
What do you observe? Do you see that the 
beam of laser light inside water follows a 
straight path? 
However, light can sometimes even bend 
around corners! This is something you will 
learn in the higher grades.
— Use a laser only under teachers’ supervision. Avoid 
using high-power lasers for this activity; a low-power laser 
pointer is su?  cient. Never point the laser beam directly at 
D
IVE
EEPER
Chapter 11.indd   156 4/3/2025   4:56:30 PM
Light: Shadows and Re? ections 
157
Fig. 11.6: Passing light 
through different materials
? List the materials of the objects in Table 11.1 and classify them 
into transparent, translucent, and opaque (In the chapter 
‘Materials Around Us’ in the Grade 6 Science textbook Curiosity
you learnt to classify materials into transparent, 
translucent, and opaque, depending on how 
you could see through them).
? Go to a dark room, turn on the torch, and place 
it at such a position that you get a spot of light 
from the torch on a wall. Or you may place a 
cardboard screen as shown in Fig. 11.6 and get 
the spot of light on it. 
? We will now conduct this activity in two 
parts — prediction and observation.
? Predict what will happen if you hold an object in front of 
the light coming out of the torch. Would you continue to 
see the spot of light on the screen? Note your prediction 
in Table 11.1.
? Now, actually place the object between the torch and 
the screen. Does light pass through the object? Note your 
observation in Table 11.1.
? Repeat this for all the objects.
Was your observation the same as your prediction? What 
conclusions could you draw? Light passes almost completely 
through transparent materials. Light passes partially through 
translucent materials. Light does not pass through opaque
materials.
What happens when an 
opaque object blocks 
the path of light?
What happens when an 
opaque object blocks 
the path of light?
11.4 Shadow Formation
What did you see on the screen in Activity 11.3 when 
an opaque object was placed in the path of light? Did 
you see a dark patch on the wall? Why was this dark 
patch formed? 
We now know that light travels in a straight line. 
So, when an opaque object is placed in its path, light is 
blocked. The dark patch, where light does not reach, 
is the shadow. 
Fig. 11.7: Shadows around us
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