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CBSE Class 8 Physics Notes for Chapter 6 Light

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CHAPTER 6 LIGHT
 
LAWS OF REFLECTION
The ray of light that strikes any surface is called the incident ray. The ray of light that comes back from the surface after reflection is called reflected ray.
A line that makes a 90o with the reflecting surface at the point where the incident ray strikes the surface is called a normal.
The angle between the normal and the incident ray is called angle of incidence.
The angle between the normal and the reflected ray is called angle of reflection.
The following are the laws of reflection:

  • The angle of incidence is equal to the angle of reflection.
  • The incident ray, reflected ray, the normal and the point of incidence all lie on the same plane.

 
REGULAR AND DIFFUSED REFLECTION
Reflection from a smooth surface is called regular reflection.
Reflection from an irregular surface is called diffused or irregular reflection.
 
HUMAN EYE
The transparent front part of the eyes is called cornea.
Behind the cornea, there is a dark muscular structure called iris.
The iris has a small opening called pupil. The size of pupil is controlled by the iris.
Behind the pupil is a lens which focuses light on the layer called retina at the back of the eye.
The retina has several nerve cells which are mainly of two types:

  • Cones: These are the cells which sensitive to bright light and sense colour.
  • Rods: These are the cells which sensitive to dim light.

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