Light

Light is a form of energy, without light you cannot see anything

Light can travel through empty spaces it travels very fast in the form of waves: The speed of light is 300,000 kilometres per second which is faster than the speed of sound

This is why, during a thunderstorm, lightning is seen before the clap of thunder is heard.

SOURCES OF LIGHT

Light comes from different things, some are natural and others are artificial.

The natural light comes from the sun, the moon, the star. these lights are not made by humans

Some lights are man-made or artificial, for example, candle, burning wood, searchlights, torch, electric bulb, and lantern

These sources are different from one another, but they all help us to see things.

PROPERTIES OF LIGHT

After being produced from a luminous object, light travels in a straight line .

A straight line along which the light travels is known as a ray of light.

A collection of rays of light is called a beam of light.

Light always travels in straight lines unless it is obstructed by something.

LUMINOUS AND NON-LUMINOUS OBJECTS

Not all objects can produce lights Objects are categorized into two types luminous and non-luminous:

•Objects that produce their own light are called luminous objects. The Sun, stars and fire are examples of luminous objects Some living things like fireflies, and many types of fishes and sea animals also produce light.

•Objects that do not produce their own light are called non-luminous objects. They can be seen because they reflect light. This light comes from luminous source.The Moon is a non-luminous object. It does not produce its own light It reflects light from the Sun.

MATERIALS AND LIGHT

Different materials allow different amounts of light to pass through them.

TRANSPARENT

They can be classified as transparent, translucent, or opaque materials. The materials which allow light to pass through them completely are called transparent materials.We can see clearly through a transparent material. The examples of transparent materials are clear plastic sheets, clear glass, air, and clean water.

TRANSLUCENT

The materials which let some light to pass through them are called translucent materials. Things can be seen through the translucent materials but not very clearly. Wax papers, frosted glass and some plastics are examples of translucent materials.

OPAQUE

The materials that do not allow light to pass through them are called opaque materials. We cannot see through an opaque material. Wood, a brick wall, and metal are opaque materials. The opaque objects form a shadow when light falls on them.

Non-luminous objects are reflective, that is, the light which falls on them come backs to you. Some objects have fuzzy or dull surfaces and others have shiny surfaces.

Dark and dull objects are poor reflectors-they absorb a lot of light. Light and shiny objects are excellent reflectors -all the light that hits them bounces back off.

The dull and shiny objects both receive the same amount of light, but they look very different.

Shadows

When a translucent or an opaque object is placed before a source of light a dark spot forms on the side opposite to light. This dark spot is called a shadow.

There are three things needed for a shadow to form:

  1. LIGHT SOURCE

  2. TRANSLUCENT OR OPAQUE OBJECT

  3. SURFACE IN WHICH A SHADOW CAN BE FORMED

CHARACTERISTICS OF SHADOWS

  • The shadow of the object forms on the opposite side from the light source.

  • A shadow shows only the shape or outline of the object.

  • Shadows do not depend on the colour of the object.

  • Opaque objects form dark shadows as they block the light completely while translucent objects form faint shadows as the objects allow light to pass through them partially

SIZE AND POSITION OF SHADOW

  • The size of the object depends on the distance between the object and the source of light.

  • The closer the object, the bigger shadow is formed.

  • The size also depends on the distance between the object and the surface where it is formed.

  • The length of the shadow depends on how high or low is the light source.

Facts

  • An object that gives out light is a source of light.

  • Moon appears bright because it reflects light from the Sun.

  • The size of the shadow depends on position of the Sun.

  • The lower the light source, the longer the shadow.

  • The higher the light source, the shorter the shadow

  • When the light source is directly above the object, the shadow will be directly underneath.