Light and OpticsA look into how we see and what we see.

What is Light?

Light is a type of wave. A wave is a disturbance that

transfers energy from one point to another without transferring matter. Eg. Water waves.

Light behaves like a special kind of wave, called an electromagnetic wave (a wave that has both electric and magnetic parts, does not require a medium, and travels at the speed of light).

The Electromagnetic Spectrum

The classification of waves is based on the energy emitted from the waves.

The visible spectrum is the sequence of colours of visible light.

There are 7 distinct colours: red, orange,

yellow, green, blue, indigo and violet.

Colour Blindness

Color blindness (color vision deficiency) is a condition in which certain colors cannot be distinguished, and is most commonly due to an inherited condition.

Red/Green color blindness is the most common form.

Color blindness seems to occur more in males.

Total color blindness (seeing in only shades of gray) is extremely rare.

There is no treatment for color blindness.

For a colour blind individual, brightness of red, orange, and yellow is much reduced compared to normal.

This dimming can be so pronounced that reds may be confused with black or dark gray.

When driving, red traffic lights may appear to be extinguished.

They may learn to distinguish reds from yellows and from greens primarily on the basis of their apparent brightness or lightness,

Violet, lavender, and purple are indistinguishable from various shades of blue.

A Comparison of a Traffic Light

Red-Green Colourblind

Colour Blind Test #1

What Number do you see?

Those who are colour blind see the number 3.

Colour Blind Test #2

What do you see?

Those who a colour blind will not see a number, just dots.

What Our Eyes See versus What is Really There...

Look at the chart and try to SAY the COLOUR.

Your right brain tries to say the colour, but your left brain insists on reading the word!

Optical Illusions

Exposes a malfunction of the visual system.

They bring out particular good adaptations of our visual system to standard viewing situations.

These adaptations are “hard-wired” in our brains, so under some artificial manipulations can cause inappropriate interpretations of the visual scene.

What Do You See?

Are the Lines Straight or Crooked?

Are the Wheels Spinning?

Can you see 10 faces in the tree?

Which Centre Dot is Larger?

Some common illusions:

Which Line is the Longest?

Can you see the face?

What do you see?

Can you see the kissing couple?

Can you see the three women?

How many Panda Bears do you see?

Does the Haze Seem to Shrink?

What Do You See?

What do you see?

How about now?

Stare at the image for 20 seconds, then look at the ceiling quickly...

What do you see?

A skull or a woman looking in a mirror?

The Magic Eye

In order to "see" the hidden image, two things must happen. First you must get one eye to look at a point in the image, while the other eye looks at the same point in the next pattern.

Second, you must hold your eyes in that position long enough for the marvellous structures in your brain to decode the 3D information that has been coded into the repeating patterns.

Can you see the image?

How about this one?