Lights and Shadow

• What is light?

Light is a source of energy. It can be an electromagnetic wave or photon (either in form of wave or small particles). Light always travels in a straight line.

• Sources of Light:

There are two types of light sources
Natural. e.g., Sunlight
Some animals having natural light producing capabilities are firefly, jelly fish. Some bacteria also produces light such as Bioluminescent bacteria
Artificial: e.g., Tube light, Neon light, Torch light, Candle light  etc.

• Types of objects

There are 3 types of objects:

1. Transparent: Which allows light to pass through it. e.g.; glass, transparent plastic sheet
2. Translucent: Which allows light to pass partially through it. e.g.; regular plastic sheet, butter paper
3. Opaque: Which does not allows light to pass through it. e.g.; wood, rock, humans

• What is a shadow?

When light is obstructed by an opaque object , the shadow is formed.
opaque object is an object which does not allow light to pass through it.

• Facts about shadows

1. The shadow is formed in the opposite direction of the light source. In the morning the sun rises in the east hence the shadow will be in the opposite direction, west. In the evening sun is setting in the west, hence shadow falls in the east direction.
2. The shadow is smallest when the light source is directly on top of the object. Thats the reason the shadows are shortest in the afternoon.
3. Lets assume there is a torch light, an object (say a doll or a cup) and the screen. The shadow becomes longer and less sharp as the object comes closer to the light source. The reverse is also true, when object is away from the light source the shadow formed is shorter and sharper.
4. Same object can form different shadows when light is positioned at different directions.
5. Similarly different objects can form same shadow based on positioning of light source.

Life cycle of plants- part 2

P5 Respiratory system notes