Science

Light (Introduction)

Light is something that many of us take for granted.
Here are some key facts about light that you need to remember:

Light travels in straight lines.

Light comes from natural and human made sources.

Objects can be transparent, translucent, or opaque.

Opaque materials form shadows

In this introduction we are going to look at the sources of Light and objects.

Light can come from two sources

Natural
Human-made

Natural
Natural light sources include the following. 
Sun, lightening, glowing rocks (lava from volcanoes) and flames. 
Some plants and animals give off light (glow worms and some deep sea fish).

Fact: did you know that the sun is so far away from Earth that it takes light over 8 minutes to get here.
So the light you see at 12.oclock left the sun at approx 11.52!

Human-made
There are a lot of sources of human made light, here are some of them: 
candles, light bulbs (in torches, around the house), televisions, fireworks.

Remember: All objects that give out their own light are called luminous (lu-min-ous).
So the sun is luminous, it is a natural light source.

Objects
Objects can be:

Transparent
Look at the table and see if you can see any patterns:

material does light go through it? shadows formed?
Clear glass yes no
perspex yes no
clear cellophane yes no

What do you notice about transparent materials?
Answer






 

 

 

 

 

 

 

 

 

 

 

 

 












They let light through and DON'T form a shadow

Translucent

Look at the table and see if you can see any patterns:

material does light go through it? shadows formed?
Patterned glass  Yes but you can't read writing through it Slight shadow
Frosted glass  Yes but you can't read writing through it Slight shadow 
Tissue paper Yes but you can't read writing through it Slight shadow 

What do you notice about translucent materials?
Answer

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


They let light through but you cannot see detail.

Opaque

Look at the table and see if you can see any patterns in opaque materials

material does light go through it? shadows formed?
wood no yes
metal no yes
plastic no yes
cardboard no yes
brick no yes

What do you notice about opaque materials?
Answer


 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 



Opaque objects do not let light through. They all form shadows.

Opaque objects can be shiny or dull.

Shiny objects reflect light very well.

Objects are anything that light hits.
For example the moon is an object that reflects light. The moon as you may know does NOT give out is own light. The moon is NOT a light source.
Do you know why the moon reflects so much light?
We will tell you at the end of this light block!
The arrows show the direction of light

Well that is it for today.

Let's review the key points:

Light travels in straight lines.

Light comes from natural and human made sources

Objects can be transparent, translucent, or opaque.

Come back again tomorrow when we will be looking at shadows.

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