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

Parts of a plant

Parts of a plant

The parts of the plants are broadly classified into various categories:

Root, Stem, Leaves, Flowers, Fruits.

The following are the different parts of the plants and their functions:

Fruit bears the seed of the plant which germinates into a seedling forming the new plant.

Life cycle of plants- Part 1

Life cycle of a plant

It is braodly classified in 3 stages:

• Seed
• Seeding
• Adult plant

But it has other stages in between as described below:

• The seed first absorbs water
• Then it gives rise to the root
• Then it gives rise to the shoot system
• Finally it forms the small plant to photosynthesise

Photosynthesis: An adult green plant needs water, air and sunlight/warmth to produce it's own food. This process is called photosynthesis (photo- meaning light, synthesis- meaning making). In photosynthesis plants takes in carbondioxide and gives out oxygen.

Respiration: It is the opposite of photosynthesis. In respiration plants takes in oxygen and gives out carbondioxide. This happens in most green plants during the night time, hence no sunlight is needed.

Singapore local science syllabus

Singapore local science syllabus 

Themes	(Primary 3 and 4)
Diversity	 Diversity of living and non-living things (General characteristics and classification)  Diversity of materials
Cycles	 Cycles in plants and animals (Life cycles)  Cycles in matter and water (Matter)
Systems	 Plant system (Plant parts and functions)  Human system (Digestive system)
Interactions	Interaction of forces (Magnets)
Energy	Energy forms and uses (Light and heat)

Life Cycle- Butterfly

Life Cycle of a Butterfly

• Butterfly is an insect and has 4 stages in it's life cycle.
• The adult female butterfly lays it's eggs on the leaves. 
• It takes about 3-7 days for a egg to hatch and produce larva.
• Larva is also called as Caterpillar.
• As soon as the larva comes out of the egg 
• First it eats it's egg shell
• Then, it starts to eat the leaves.
• The larva grows and undergoes a process called as molting to form Pupa. It takes about 2-5 weeks for larva to become Pupa.
• Molting is a process of shedding of outer skin. In the entire life cycle of a butterfly it happens 5 times.
• Between formation of larva and pupa, molting happens 4 times. The butterfly keeps growing in size after each molting.
• After 4th molting the larva stops growing and forms a protective layer around it. This stage is called pupa stage or chrysalis.
• It takes about 15 days for a pupa to become an adult butterfly. The 5th and the final molting occurs at the end of pupa stage forming the adult butterfly.
• As soon as the butterfly comes out of the chrysalis it's
• wings are small
• wings are wet
• The butterfly pumps fluid to it's wings to make the wings bigger and stronger.
• It takes about 2 hours for a new born butterfly to become a fully grown strong butterfly.
• The changes that happen during the entire life cycle of an animal is called metamorphosis. It is also called as transformation.