Remember, as a member of the Science Bus Club you can ‘Ask Albert’ a question about any of the topics. So if you’re not already a member join today!!
How Light Travels
Light travels very, very fast. It travels at 299,792,458 meters every second. Light travels in a straight line.
Here are some useful words for you to know:
Opaque - A material that light cannot pass through
Reflect - That’s what happens to light when it ‘bounces’ off a surface in particular shiny surfaces such as mirrors
Reflection - It’s what you see when you look into a mirror.
Mirror - A very shiny surface that reflects light, have you a mirror in your bedroom?
You learned before that because light travels in straight line shadows are created when it hits an object.
Different Types Of Water
Light enters our eye through the
pupil, the black hole in the middle. It is focused by a
lens onto the back of the eye. This area is called the
retina. The retina changes the light into electrical signals which travel to our brain along the
optic nerve. Where the optic nerve leaves the back of the eye we have a blind spot.
You can do a simple experiment to show this:
On a piece of paper mark two dots approximately 2 inches apart.- Now look at the dots at arms length and looking at the left dot bring the paper slowly towards your face.
- When one of the dots you are looking at gets focussed onto where the optic nerve is, the spot disappears.
Cool!!!
Below is a diagram of the eye:
Beams Of Light
Light travels in straight lines. If you shine a torch in a mirror you see the light reflected back at you. Now shine the torch at different angles. The reflected light come back at you at the same angle it went in. With mirrors you can see around corners.
Periscopes
Did you ever see a periscope in a submarine? That uses mirrors to see above the water.
Below is a picture of a periscope:
Make A Periscope
Have you ever wanted to be able to see what's on top of the refrigerator or around the corner? Now, you can, using the same method submariners use to see above the water's surface while they are submerged.
All you need is:
A long narrow box - 2 small square mirrors
- Scissors
Here's what you do:
First, we are going to make the view holes. Do this by cutting two rectangular holes in the box - one at the top and the other at the bottom on the opposite side.
- Next, we need to insert the mirrors. These should be set at 45-degree angles opposite each hole. You can cut slits in the sides to insert the mirrors and use tape to hold them in place.
- Now, you can spy on your siblings around corners or see if the grass really is greener on the other side of that tall fence!
Here's how it works:
Images in front of the top hole are reflected from the top mirror into the bottom mirror where they can be seen through the bottom hole. Submarine periscopes operate very much the same way except on a bigger scale and with magnifiers to help Submariners view distant objects clearly.
Make A Periscope
Shadows come about when light travelling from a light source is blocked. Peter Pan thought he could catch his own shadow but that we know is impossible!
Have you ever seen your shadow on a sunny day? The light from the sun is blocked and the area you are blocking appears as a shadow on the ground. The sun is the source of light and you are the object blocking it. Can you think of any other sources of light? How about a torch? That’s a source of light and will still cast a shadow.
Have you ever heard of a lunar eclipse? That is when the earth blocks the light from the sun and casts a shadow that stretches all the way to the moon.
When your shadow is caused by the sun it will change during the course of the day as the earth rotates varying the angle the light hits you. As the angle becomes more obtuse the longer your shadow will become.
Try this experiment
On a sunny day go out into your school playground or garden and stand so that your shadow appears on the ground.
Now mark out either with chalk or with sticks a) exactly where you are standing b) mark out your shadow.
Continue doing this every hour remembering to stand exactly in the same place repeatedly marking your shadow each time.
At the end of the day you will see how your shadow moved across the ground.
As the earth moved so did your shadow as each hour went by the source of light was arriving and hitting you at a different angle. To complete this experiment use a chart to plot a the time of day the length of your shadow
Note - Click on the flash window above to activate it
Remember, as a member of the Science Bus Club you can ‘Ask Albert’ a question about any of the topics. So if you’re not already a member join today!!
