What makes the things visible
During the day, the sunlight helps us to see objects. An object reflects light that falls on it.
This reflected light, when received by our eyes, enables us to see things.
eye
source
object
Luminous object
Non Luminous object
Luminous object- An object which possesses light of its own Ex. Sun , Stars Bulb , candle, lamp.
Non-Luminous object- An object which does not possesses light of its own Ex. Moon. planets,
Book, Table, Chair
What is light
Light is a form of energy that allows us to see the world around us. It is a type o
electromagnetic wave which has the electric field and magnetic field are perpendicul
to each other and both are perpendicular to the direction of the wave propagation.
Wavelengths between 380 and 750 nanometers, which are visible to the human eye.
The speed of light in vacuum is
Vair > Vwater(2.25 x 10^8m/s) > Vglass(2 x 10^8m/s).
Light trave from one point to another point in a straight line.
The frequency of light remains same in all the mediums.
Light makes shadow. Without light Shadow is not possible.
It is a non-mechanical wave as it doesn't require any medium to travel.
PARTICLE THEORY OF LIGHT:
According to Newton, light travels in space with a great speed as a stream of very small particles
called corpuscles. If the dimensions of the object is very large as comparable to the wavelength
of light then light behaves as particle. This theory failed to explain the interference of light as
well as the diffraction of light. So a wave theory of light was accepted.
WAVE THEORY OF LIGHT:
According to the wave theory, light consists of electromagnetic waves. The light waves travel
with a very high speed of 3 × 108 m/s in vacuum.
The wavelength of visible light waves lies between 380 and 750 nanometers
If the dimensions of the object is very very small and comparable to the wavelength of light then
light behaves as wave. The phenomenon of diffraction (bending of light around the corners of tiny
objects) interference and polarization of light can only be explained if the light is considered to
be of wave nature.
, The dictionary definition of LIGHT is "something that makes things visible or affords
illumination," a vague and unsatisfying definition that circles around like a dog chasing
its own tail. Physicists define light as electromagnetic radiation- a travelling energy
wave
.
Light itself is invisible but it helps us to see the beautiful world around us. The bright colour
of flowers, butterflies, feathers of a peacock, the rainbow, the blue colour of the sky, the
reddish colour of the sunrise and sunset and spectacular beauty of nature. To understand this,
let us take a step forward by studying "Light Reflection and Refraction. The branch of physics
which deals with the nature of light, its sources, properties, effects and vision is called optics.
Propagation of Light:
It travels along a straight line. Its path charges only when something comes in its path or when
there is a change of medium. This is called rectilinear propagation of light. Light that originates
from a point P and passes through another point Q in the same medium actually passes through all
the points on the straight line PQ. This straight line path of light is called a ray of light. A bundle
of light rays is called a beam of light.
P Q
Ray of light Beam of light
A black board appears black because most of light incident on it is absorbed by it. An objec
that allows light to pass through it is called transparent.
Ordinary glass sheet transmits most of light falling on it so it appears transparent
But some surface reflect most of the light falling on them and are called reflecting surfaces,
A polished silver mirror reflects light falling on it.
An object that does not allow light to pass through it is known as opaque medium e.g, stone, met
sheets etc.
, ELECTROMEGNETIC SPECTRUM
Many types of radiations in the form of wave are released from the sun, star and are travelled i
the form of electromagnetic waves.
radio
ROYGBIV
Energy increasing
frequency increasing
Wavelength decreasing
Velocity constant
The portion of electromagnetic wave which are visible to human eyes is called light.it contain
seven colors. V I B G Y O R. The color of any object we see is determined by the specifi
wavelengths of light that are reflected back by that object to our eyes.
White Light Red
RED
White Light Blue
White Light
White Light All
BLUE
Black
White
During the day, the sunlight helps us to see objects. An object reflects light that falls on it.
This reflected light, when received by our eyes, enables us to see things.
eye
source
object
Luminous object
Non Luminous object
Luminous object- An object which possesses light of its own Ex. Sun , Stars Bulb , candle, lamp.
Non-Luminous object- An object which does not possesses light of its own Ex. Moon. planets,
Book, Table, Chair
What is light
Light is a form of energy that allows us to see the world around us. It is a type o
electromagnetic wave which has the electric field and magnetic field are perpendicul
to each other and both are perpendicular to the direction of the wave propagation.
Wavelengths between 380 and 750 nanometers, which are visible to the human eye.
The speed of light in vacuum is
Vair > Vwater(2.25 x 10^8m/s) > Vglass(2 x 10^8m/s).
Light trave from one point to another point in a straight line.
The frequency of light remains same in all the mediums.
Light makes shadow. Without light Shadow is not possible.
It is a non-mechanical wave as it doesn't require any medium to travel.
PARTICLE THEORY OF LIGHT:
According to Newton, light travels in space with a great speed as a stream of very small particles
called corpuscles. If the dimensions of the object is very large as comparable to the wavelength
of light then light behaves as particle. This theory failed to explain the interference of light as
well as the diffraction of light. So a wave theory of light was accepted.
WAVE THEORY OF LIGHT:
According to the wave theory, light consists of electromagnetic waves. The light waves travel
with a very high speed of 3 × 108 m/s in vacuum.
The wavelength of visible light waves lies between 380 and 750 nanometers
If the dimensions of the object is very very small and comparable to the wavelength of light then
light behaves as wave. The phenomenon of diffraction (bending of light around the corners of tiny
objects) interference and polarization of light can only be explained if the light is considered to
be of wave nature.
, The dictionary definition of LIGHT is "something that makes things visible or affords
illumination," a vague and unsatisfying definition that circles around like a dog chasing
its own tail. Physicists define light as electromagnetic radiation- a travelling energy
wave
.
Light itself is invisible but it helps us to see the beautiful world around us. The bright colour
of flowers, butterflies, feathers of a peacock, the rainbow, the blue colour of the sky, the
reddish colour of the sunrise and sunset and spectacular beauty of nature. To understand this,
let us take a step forward by studying "Light Reflection and Refraction. The branch of physics
which deals with the nature of light, its sources, properties, effects and vision is called optics.
Propagation of Light:
It travels along a straight line. Its path charges only when something comes in its path or when
there is a change of medium. This is called rectilinear propagation of light. Light that originates
from a point P and passes through another point Q in the same medium actually passes through all
the points on the straight line PQ. This straight line path of light is called a ray of light. A bundle
of light rays is called a beam of light.
P Q
Ray of light Beam of light
A black board appears black because most of light incident on it is absorbed by it. An objec
that allows light to pass through it is called transparent.
Ordinary glass sheet transmits most of light falling on it so it appears transparent
But some surface reflect most of the light falling on them and are called reflecting surfaces,
A polished silver mirror reflects light falling on it.
An object that does not allow light to pass through it is known as opaque medium e.g, stone, met
sheets etc.
, ELECTROMEGNETIC SPECTRUM
Many types of radiations in the form of wave are released from the sun, star and are travelled i
the form of electromagnetic waves.
radio
ROYGBIV
Energy increasing
frequency increasing
Wavelength decreasing
Velocity constant
The portion of electromagnetic wave which are visible to human eyes is called light.it contain
seven colors. V I B G Y O R. The color of any object we see is determined by the specifi
wavelengths of light that are reflected back by that object to our eyes.
White Light Red
RED
White Light Blue
White Light
White Light All
BLUE
Black
White
