Let's take a closer look at Light...

Were you ever scared of the dark as a child? No real surprise there, we are creatures of the light, millions of years of evolution has taught us to fear the dangers lurking in the dark. Light is very important to us, we do not see that well in the dark, and our images are the same, if they are not well lit, it is difficult to see the details. But have you ever actually taken the time to understand Light? Why do some things appear as different colours? How does it travel? Why does it move so quickly?

Don't panic... I am not about to get all Geek or science'y' on you here, just the basics.

  • Light arrives on our planet after a quick trip from the Sun, 149 million km (93 million miles away). Light travels at 186,000 miles (300,000 km) per second, so the light you're seeing now was still at the Sun about eight minutes ago.

  • The Sun is a nuclear fireball spewing energy in all directions. We simply see that light as one part of the energy that the Sun makes, the part we can detect with our eyes. When light travels between two places (from the Sun to the Earth), it is the energy making a journey between those two points. 

  • Light behaves in four rather interesting and useful ways that we describe as reflection, refraction, diffraction, and interference...

    Reflection

    The first thing we often notice about light is that it will reflect off things. The reason we can see the things around us is because of light, either from the Sun or from something like an a lightbulb, is it reflects off them into our eyes. Turn off the light or stop the light reaching our eyes (Blindfold or at Night)and those objects disappear. They don't cease to exist, but you can no longer see them. Like walking around an unfamiliar room with the lights off.

    Reflection can happen in two different ways. If you have a smooth surface and you shine a narrow beam of light at it, you get a narrow beam of light reflected back off it. This is called specular reflection. Most objects aren't smooth, and are quite rough. So, when you shine light onto them, it's scattered all over the place. This is called diffuse reflection and it's how we see most objects around us as they scatter the light falling on them.

    Example: Polish up a teaspoon and you can see your face quite clearly. If you can see your face in something, it's specular reflection. But if the spoon is dirty, all the bits of dirt and dust are scattering light in all directions and your face disappears, if you can't see your face, it's diffuse reflection.

    Try it...

JuliePowell_Reflection.jpg

Refraction

Light travels in straight lines through space, but interesting things can happen when they travel through other materials—especially when they move from one material to another. No matter how hard you try, you cannot run as quickly through water as through air. The dense liquid is harder to push out of the way, so it slows you down. Same thing happens when you shine light through water glass or plastic, but it appears makes the light bend - Refraction

Example put a straw in half a glass of water, it will look like it is at a different angle in water than above...Try It.

JuliePowell_Refraction.jpg

Diffraction

Light cannot bend around corners of object the way sound can travel, you can hear something around a corner without actually seeing it right? Sound waves spread out differently that Light Waves although it can spread out if your shine it through a small aperture. This is called Diffraction. Close your eyes almost shut and look at a streetlight in the dark. As your eyes close, the light seems to spread out in strange stripes as it squeezes through the narrow gaps between your eyelids and eyelashes. The tighter you close your eyes, the more the light spreads (until it disappears when you close your eyes completely).

JuliePowell_Defraction.jpg

Interference

If you stand above a glass of water and dip your finger in, then allow a single drop to drip down to the water surface, you'll see ripples of energy spreading outwards from the point of the impact. If you do this in two different places, the two sets of ripples will move toward one another, crash together, and form a new pattern of ripples called an Interference Pattern. Light behaves in exactly the same way. If two light sources produce waves of light that travel together and meet up, the waves will interfere with one another where they cross. In some places the waves will unit and get bigger, but in other places one wave will meet another wave and the two will cancel out.

Interference causes effects like the swirling, colored spectrum patterns on the surface of soap bubbles and the similar rainbow effect you can see if you hold a compact disc up to the light. Interference is very colorful, but it has practical uses too.

JuliePowell_Interference.jpg

So WHY do we see different colours?

Colour is one of the coolest, but weird things about light. Think about this - if we see things because sunlight is reflected off them, how come everything isn't the same color? Why isn't everything the color of sunlight? Well...Sunlight isn't light of just one color, what we normally see we call white light, is made up of all the different colors mixed together, when we refract (or bend) the light, say with a prism or a rainbow, we can see all the different colours.

So why does a red apple look red? When sunlight shines on a apple, the red part of the sunlight is reflected back again off the apple's skin, while all the other colors of lights are absorbed by the apple, so you don't see them.

If you shined a light through a piece of green plastic at the red apple it would appear black, because the apple would absorb the green light. At Night if you go out to the garden everything appears in shade of grey, because there is very little light to reflect the colour.

Now that the Science bit is out of the way...time to have a break, grab a cuppa and let's get to the fun bits...learning to use light to make great photos.

Want to join us?