Physics Notes

8th physics light reflection refraction eyes defect and dispersion
The ray of light which falls on the mirror surface is called incident ray.
The point at which the incident ray strikes the mirror is called the point of incidence.
The ray of light which is sent back by the mirror is called the reflected ray.
The ‘normal’ is a line drawn at right angles to the mirror surface at the point of incidence.
The angle between incident ray and normal is called the angle of incidence.
The angle between reflected ray and normal is called the angle of reflection.Laws of reflection of light:
 The incident ray, the reflected ray, and the normal {at the point of incidence}, all lie in the same plane.
 The angle of reflection is always equal to the angle of incidence.
Regular Reflection and Diffuse Reflection of Light
Regular Reflection In regular reflection, a parallel beam of incident light is reflected as a parallel beam in one direction.
• Regular reflection of light occurs from smooth surfaces like that of a plain mirror.
• Images are formed by regular reflection of light.
Diffused Reflection In Diffuse reflection, a parallel beam of incident light is reflected in different directions.
 The diffuse reflection of light takes place from rough surfaces
 A sheet of paper produces diffuse reflection of light. No image is formed in diffuse reflection of light.
Characteristics of image formed by a plane mirror
 The image formed by a plane mirror is virtual & Erect.
 The image formed in a plane mirror is the same distance behind the mirror as the object is in front of it.
 The image formed in a plane mirror is of the same size as the object.
 The image in a plane mirror is laterally inverted.
Periscope : A Periscope is a device through which a person can se the objects that are out of the direct line of sight. For example, by using a periscope, we can see the objects on the other side of a high wall which cannot be seen by us