Light | Reflection of Light | Laws of reflection | Classs 10 physics

Light | Reflection of Light | Laws of reflection | Classs 10 physics

Here we study class 10 physics,optics,light,reflection of light,laws of reflection,plane mirror,reflection by plane mirror,theory of light.

Light

1. Light is a form of energy which enables us to see an object.

2.It is an electromagnetic wave.

3.Light waves are transverse in nature.

4.Light waves are electromagnetic radiation so they do not need a material medium to  travel.

5.It travels in vacuum as well as in material transparent medium.

6. The speed of light is 300000km/s in vacuum.

7.The speed of light in material medium is less than in vacuum.

8. Light travels in a  straight line.

9.Light is the fastest messenger in the universe.

Theory of Light

There are four theories of light. These are

1.Newton's Corpuscular Theory of Light

 : It explains corpuscles/particles nature of light.It proves rectillinear propagation of light, Reflection of light,Refraction of light. It does not prove interference of light,diffraction of light, polarization of light etc.

2. Huyghen's Wave Theory of light

: It explains wave nature of light. This theory proves rectilinear propagation of light,reflection of light,refraction of light,interference of light,diffraction of light,polarization of light. But it does not prove photoelectric effect of light,chrompton,stark effect of light.

3.Quantum Theory of Light

:It explains particle nature of light.The light emitted by a source in the form a particle called photon.The energy of a photon is equal to the product of plank's constant and frequency of light. It explains photoelectric effect of light, chrompton's effect and stark's effect.

4.It explains dual nature of light.Light sometimes behaves like a particle and sometimes as a wave.

Reflection of Light

1.When a ray of light coming from a medium strikes a surface it returns back back in the same medium.This phenomenon of light is called reflection of light.

2. Reflection is the phenomenon of bouncing back of light into the same medium on

striking the surface of any object.

Kinds of reflection

: There are two types of reflection. These are

1. Regular Reflection

 : The reflection shown by a plane surface is called regular reflection.

2. Irregular reflection or Diffused reflection

: The reflection shown by a rough surface is called Diffused reflection.

 Laws of Reflection

 First law: The incident ray, the normal to the surface at the point of incidence and

the reflected ray, all,lie in the same plane.

Second law: The angle of reflection (r) is always equal to the angle of incidence(i).

i.e. ∠i = ∠r

Formation of image by a plane mirror :

The schematic ray diagram of formation of image by a plane mirror is shown in figure .Here O is point object whose virtual and erect image is I . The size of image is equal to the size of object.

Features of image formed by a plane mirror

:The image formed by a plane mirror is always

1.virtual and erect

2. of the same size as the object

3. as far behind the mirror as the object is in front of it

4. laterally inverted

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