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.