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Science
LIGHT ,SHADOWS AND REFLECTION
LIGHT SHADOWS AND REFLECTION
1.Introduction
1. Light is form of energy which gives us the sensation of light.
Without light we cannot see the object, it helps us to see the objects.
2. Light does not require a material medium for its propagation. In a
given medium light travels with a very high but finite velocity. The
velocity of light in air or vacuum is 3 x 108 m/s.
2. Luminous and Non-luminous objects

Luminous objects
Objects that emit light on their own are called luminous objects.
Examples are a tube light, the sun, a lit candle, glowing bulb, a
bonfire and a lit torch.

Non-luminous objects
Objects that do not emit light on their own are called non –luminous
objects.. Examples are the moon, a book, a pen, a wooden box, a
cupboard and a chair.
SHADOW FORMATION : When an opaque object comes in path of
light shadow is formed. Formation of Shadows
Ø An opaque object blocking the path of light is called a
shadow.
:- A shadow is a dark region, and is formed only when
1- a light source,
2- an opaque object and
3- a screen are present.
Ø For example, during a lunar eclipse, we see a part of the
earth’s shadow on the surface of the moon.
Ø This happens when the earth, the sun and the moon are in a
straight line, with the earth between the sun and the moon.
Here, the sun acts as the light source, the earth as the
opaque object, and the moon as the screen.
Ø Opaque objects form shadows because light is not able to
bend around them.
Ø Whatever the colour of the object, its shadow is always black
because it is not illuminated by light.
For example, during a lunar eclipse, we see a part of the earth’s
shadow on the surface of the moon.
PINHOLE CAMERA: The device which forms a photograph like
image of bright objects on a screen is called pinhole camera.
REFLECTION OF LIGHT: Bouncing back of light after striking a
shiny surface is called reflection
A transparent object is something that will allow all of
the light rays to pass through it. Things like glass, some kids of
plastic and food wrappers are transparent because of the density of
the molecules inside it.
examples: air ,clean water,glass etc.
A translucent object is a material that will only allow
some or a little bit of the light rays to pass through it. Things like
wax paper, cloth and butter paper are translucent because of the
density of the molecules inside it.
examples: tracing- paper, kite- paper, ice , polythene , ground glass, etc.
An opaque object is something that will allow no light to
pass through it because the density of the object is too great.
Things like wood folders and mirrors are opaque.
examples: stone, wood ,rubber, metal ,soil etc.
The difference between transparent, translucent, and opaque
objects is that opaque objects are denser in molecules than
translucent objects and that translucent object are denser than
transparent objects. Transparent objects let all the light rays pass
through. Translucent objects are denser therefore allowing only
some light rays to pass through because some are ether being
absorbed or reflected. Opaque objects don't allow any light rays to
pass through because all of the light rays are being reflected or
absorbed.
ADDITIONAL INFORMATION
In the olden days, shadows caused by objects placed in the sun
were used to measure time. Such a device is called a sun
dial.
The Jantar Mantar in Jaipur consists of a sundial or Samrat
Yantra, which can be used to tell the time.
Pinhole Camera
The image formed by a pinhole camera is inverted and smaller
in size when compared to the original object.
These cameras work on the principle that light travels in a
straight line. Pinhole cameras are cheap and simple to make.
An eclipse can be viewed using a pinhole camera.
Mirrors and reflections
The likeness of an object carried and formed by light in a mirror
is called an image. For example, your image is a reflection of
your face in the mirror.
An image can be seen in the mirror because the light reflected
from an object falls on the mirror and it is reflected.
This bouncing of light by any smooth surface is called reflection
of light. Mirrors change the direction of light incident on
them.
The image in a plane mirror is the same size and colour as that of
the object. Moreover, the distance between the image and the
mirror, is the same as the distance between the mirror and the
object.
Science
LIGHT ,SHADOWS AND REFLECTION
LIGHT SHADOWS AND REFLECTION
1.Introduction
1. Light is form of energy which gives us the sensation of light.
Without light we cannot see the object, it helps us to see the objects.
2. Light does not require a material medium for its propagation. In a
given medium light travels with a very high but finite velocity. The
velocity of light in air or vacuum is 3 x 108 m/s.
2. Luminous and Non-luminous objects

Luminous objects
Objects that emit light on their own are called luminous objects.
Examples are a tube light, the sun, a lit candle, glowing bulb, a
bonfire and a lit torch.

Non-luminous objects
Objects that do not emit light on their own are called non –luminous
objects.. Examples are the moon, a book, a pen, a wooden box, a
cupboard and a chair.
SHADOW FORMATION : When an opaque object comes in path of
light shadow is formed. Formation of Shadows
Ø An opaque object blocking the path of light is called a
shadow.
:- A shadow is a dark region, and is formed only when
1- a light source,
2- an opaque object and
3- a screen are present.
Ø For example, during a lunar eclipse, we see a part of the
earth’s shadow on the surface of the moon.
Ø This happens when the earth, the sun and the moon are in a
straight line, with the earth between the sun and the moon.
Here, the sun acts as the light source, the earth as the
opaque object, and the moon as the screen.
Ø Opaque objects form shadows because light is not able to
bend around them.
Ø Whatever the colour of the object, its shadow is always black
because it is not illuminated by light.
For example, during a lunar eclipse, we see a part of the earth’s
shadow on the surface of the moon.
PINHOLE CAMERA: The device which forms a photograph like
image of bright objects on a screen is called pinhole camera.
REFLECTION OF LIGHT: Bouncing back of light after striking a
shiny surface is called reflection
A transparent object is something that will allow all of
the light rays to pass through it. Things like glass, some kids of
plastic and food wrappers are transparent because of the density of
the molecules inside it.
examples: air ,clean water,glass etc.
A translucent object is a material that will only allow
some or a little bit of the light rays to pass through it. Things like
wax paper, cloth and butter paper are translucent because of the
density of the molecules inside it.
examples: tracing- paper, kite- paper, ice , polythene , ground glass, etc.
An opaque object is something that will allow no light to
pass through it because the density of the object is too great.
Things like wood folders and mirrors are opaque.
examples: stone, wood ,rubber, metal ,soil etc.
The difference between transparent, translucent, and opaque
objects is that opaque objects are denser in molecules than
translucent objects and that translucent object are denser than
transparent objects. Transparent objects let all the light rays pass
through. Translucent objects are denser therefore allowing only
some light rays to pass through because some are ether being
absorbed or reflected. Opaque objects don't allow any light rays to
pass through because all of the light rays are being reflected or
absorbed.
ADDITIONAL INFORMATION
In the olden days, shadows caused by objects placed in the sun
were used to measure time. Such a device is called a sun
dial.
The Jantar Mantar in Jaipur consists of a sundial or Samrat
Yantra, which can be used to tell the time.
Pinhole Camera
The image formed by a pinhole camera is inverted and smaller
in size when compared to the original object.
These cameras work on the principle that light travels in a
straight line. Pinhole cameras are cheap and simple to make.
An eclipse can be viewed using a pinhole camera.
Mirrors and reflections
The likeness of an object carried and formed by light in a mirror
is called an image. For example, your image is a reflection of
your face in the mirror.
An image can be seen in the mirror because the light reflected
from an object falls on the mirror and it is reflected.
This bouncing of light by any smooth surface is called reflection
of light. Mirrors change the direction of light incident on
them.
The image in a plane mirror is the same size and colour as that of
the object. Moreover, the distance between the image and the
mirror, is the same as the distance between the mirror and the
object.