The definition and the characteristic of light

A. The definition of Light

In daily life, light has an important role. We can see the object because light is reflected from the object to our eyes. When we looked into the mirror, we will see our image so that we can tidy-up our clothes and hair. Is it possible for us to look our self in the mirror, read a book, or see an object in a dark room?
Light travels in a straight line in a vacuum or uniform medium.

Light can be defined as a form of energy. Light help us to see things. The Sun, the stars and the glowworm are some of the natural sources of light, whereas, oil lamps, candles, electric lights are examples of artificial source of light. Objects that given off their own light are called luminous objects and objects that do not given off their own light are called the non-luminous objects. The non-luminous objects can be seen due to the light reflected by them.

A. Defining of Light
Light travels in a straight line. This property is called the rectilinear propagation of light.
Light As one of electromagnetic wave and light travels at a speed of about 3 x 108 m/s in vacuum. Its speed reduces while traveling through denser mediums like water, glass etc.
B. Characteristics of the Light
1. To spread without trough medium
2. Travels in straight line
3. Can be reflected
4. Can be refracted

C.The effect of the light to travel in straight line

1.I1. Its occurred the nucleus shadows (umbra)

2.2. Its occurred the add shadows ( penumbra)

3. Examples :

1.4. Eclipse of lunar

2.5. Eclipse of sun