PPT- Light Class 7 PPT

 Page 1


Light 
Name: Mohammed Ashfan Ahmed Mallick
Class: VII
Section: A
Subject Teacher: Anita Singh
Light
Page 2


Light 
Name: Mohammed Ashfan Ahmed Mallick
Class: VII
Section: A
Subject Teacher: Anita Singh
Light
Light And How Does It Travels In A Straight Line
• Light is a naturally occurring substance that enhances vision and makes objects visible. Sun is the natural source of light.
Travelling Of Light In A Straight Line:
? The path of light gets blocked when an object covers the source of light.
? This is illustrated by trying to see the flame of a candle using a straight pipe and then with a bent pipe. This proves that 
light travels in a straight line. Travelling of light in a straight line, is also known as Rectilinear Propagation Of Light 
Based On Their Interaction With Light, Objects Can Be Classified As:
• Transparent objects allow light to pass through them completely
Example: Glass
• Translucent objects allow light to pass through them partially. 
Example: Butter Paper
• Opaque objects do not allow any light to pass through them. 
Example: Book
Page 3


Light 
Name: Mohammed Ashfan Ahmed Mallick
Class: VII
Section: A
Subject Teacher: Anita Singh
Light
Light And How Does It Travels In A Straight Line
• Light is a naturally occurring substance that enhances vision and makes objects visible. Sun is the natural source of light.
Travelling Of Light In A Straight Line:
? The path of light gets blocked when an object covers the source of light.
? This is illustrated by trying to see the flame of a candle using a straight pipe and then with a bent pipe. This proves that 
light travels in a straight line. Travelling of light in a straight line, is also known as Rectilinear Propagation Of Light 
Based On Their Interaction With Light, Objects Can Be Classified As:
• Transparent objects allow light to pass through them completely
Example: Glass
• Translucent objects allow light to pass through them partially. 
Example: Butter Paper
• Opaque objects do not allow any light to pass through them. 
Example: Book
Reflection And 
Its Laws 
• When light is incident on a certain surface, it either gets reflected 
or bounces back. Such surfaces are well polished and act like a mirror. 
The phenomenon of light bouncing off surfaces is called reflection.
Laws
• The ray of light that strikes a reflecting surface is called as the incident 
ray and the ray that gets reflected back is called the reflected ray
• The imaginary line that is perpendicular to the reflecting surface at the 
point of incidence is called the normal
• Angle of incidence ?i is the angle between the incident ray and the 
normal. Angle of reflection ?r is the angle between the reflected ray and 
the normal.
• Law of Reflection states that the Angle Of Incidence {?i }, is always equal 
to the Angle Of Reflection {?r }(?i = ?r).
• The Angle Of Incidence {?i } and Angle Of Reflection the normal all lie on 
the same plane.
Page 4


Light 
Name: Mohammed Ashfan Ahmed Mallick
Class: VII
Section: A
Subject Teacher: Anita Singh
Light
Light And How Does It Travels In A Straight Line
• Light is a naturally occurring substance that enhances vision and makes objects visible. Sun is the natural source of light.
Travelling Of Light In A Straight Line:
? The path of light gets blocked when an object covers the source of light.
? This is illustrated by trying to see the flame of a candle using a straight pipe and then with a bent pipe. This proves that 
light travels in a straight line. Travelling of light in a straight line, is also known as Rectilinear Propagation Of Light 
Based On Their Interaction With Light, Objects Can Be Classified As:
• Transparent objects allow light to pass through them completely
Example: Glass
• Translucent objects allow light to pass through them partially. 
Example: Butter Paper
• Opaque objects do not allow any light to pass through them. 
Example: Book
Reflection And 
Its Laws 
• When light is incident on a certain surface, it either gets reflected 
or bounces back. Such surfaces are well polished and act like a mirror. 
The phenomenon of light bouncing off surfaces is called reflection.
Laws
• The ray of light that strikes a reflecting surface is called as the incident 
ray and the ray that gets reflected back is called the reflected ray
• The imaginary line that is perpendicular to the reflecting surface at the 
point of incidence is called the normal
• Angle of incidence ?i is the angle between the incident ray and the 
normal. Angle of reflection ?r is the angle between the reflected ray and 
the normal.
• Law of Reflection states that the Angle Of Incidence {?i }, is always equal 
to the Angle Of Reflection {?r }(?i = ?r).
• The Angle Of Incidence {?i } and Angle Of Reflection the normal all lie on 
the same plane.
Activity { For Reflection } And Images 
• ?AOX is called the angle of 
incidence. 
• ?BOX is called the angle of 
reflection.
• ?MON is called the normal. 
We Can Say That The 
Reflected Ray Leaves The 
Mirror At The Same Angle At 
Which Incident Ray Strikes It. 
• Rays of light from an object 
after reflection by a mirror 
tend to converge or appear 
to diverge from a certain 
point in front of the mirror. 
This copy of the object is 
called an image. 
Page 5


Light 
Name: Mohammed Ashfan Ahmed Mallick
Class: VII
Section: A
Subject Teacher: Anita Singh
Light
Light And How Does It Travels In A Straight Line
• Light is a naturally occurring substance that enhances vision and makes objects visible. Sun is the natural source of light.
Travelling Of Light In A Straight Line:
? The path of light gets blocked when an object covers the source of light.
? This is illustrated by trying to see the flame of a candle using a straight pipe and then with a bent pipe. This proves that 
light travels in a straight line. Travelling of light in a straight line, is also known as Rectilinear Propagation Of Light 
Based On Their Interaction With Light, Objects Can Be Classified As:
• Transparent objects allow light to pass through them completely
Example: Glass
• Translucent objects allow light to pass through them partially. 
Example: Butter Paper
• Opaque objects do not allow any light to pass through them. 
Example: Book
Reflection And 
Its Laws 
• When light is incident on a certain surface, it either gets reflected 
or bounces back. Such surfaces are well polished and act like a mirror. 
The phenomenon of light bouncing off surfaces is called reflection.
Laws
• The ray of light that strikes a reflecting surface is called as the incident 
ray and the ray that gets reflected back is called the reflected ray
• The imaginary line that is perpendicular to the reflecting surface at the 
point of incidence is called the normal
• Angle of incidence ?i is the angle between the incident ray and the 
normal. Angle of reflection ?r is the angle between the reflected ray and 
the normal.
• Law of Reflection states that the Angle Of Incidence {?i }, is always equal 
to the Angle Of Reflection {?r }(?i = ?r).
• The Angle Of Incidence {?i } and Angle Of Reflection the normal all lie on 
the same plane.
Activity { For Reflection } And Images 
• ?AOX is called the angle of 
incidence. 
• ?BOX is called the angle of 
reflection.
• ?MON is called the normal. 
We Can Say That The 
Reflected Ray Leaves The 
Mirror At The Same Angle At 
Which Incident Ray Strikes It. 
• Rays of light from an object 
after reflection by a mirror 
tend to converge or appear 
to diverge from a certain 
point in front of the mirror. 
This copy of the object is 
called an image. 
Real And Virtue Image 
• A real image is formed by the actual 
crossing of light rays after reflection. Real 
images can be viewed on a screen.
• A virtual image is the plain crossing of 
diverging light rays after reflection. Virtual 
images cannot be viewed on a screen.
• The image formed by a plane mirror is 
erect, virtual and is of the same size as the 
object. The image is at the same distance 
behind the mirror as the object is in front 
of it.