1. Light and Color
Standard: S8P4c. Explain how the human eye sees objects and colors in terms of wavelengths.
EQ: How do humans like yourself see color?

2. Part 1 – Properties of Light
Light travels in straight lines:
Laser

3. Light travels VERY FAST – around 300,000 kilometres per second.
At this speed it can go around the world 8 times in one second.

4. Light travels much faster than sound. For example:
Thunder and lightning start at the same time, but we will see the lightning first.
2) When a starting pistol is fired we see the smoke first and then hear the bang.

5. The Electromagnetic Spectrum
The electromagnetic spectrum represents the range of energy from low energy, low frequency radio waves with long wavelengths up to high energy, high frequency gamma waves with small wavelengths.

6. Visible Light
Visible light is a small portion of this spectrum. This is the only part of this energy range that our eyes can detect. What we see is a rainbow of colors. Each color has a different wavelength that our eyes register.

7. Color ROY G BIV is the order…. From longest wavelength to shortest
From lowest frequency to highest
From lowest energy to highest
These 7 colors combined make up white light which is light from the sun (radiant energy).

8. Color
White light is not a single color; it is made up of a mixture of the seven colors of the visible light spectrum.
We can demonstrate this by splitting white light with a prism:
This is how rainbows are formed: sunlight is “split up” by raindrops.

9. We see objects because the objects reflect light into our eyes:
How do we see objects?
We see objects because the objects reflect light into our eyes:
Homework

10. How do we see Color?
1. All the colors of the visible light spectrum shine on the apple. 2. The surface of a red apple absorbs all of the other colors of the spectrum, except for red, and reflects red to the human eye. 3. Humans would not be able to see color or objects without LIGHT!! Light has to reflect off an object in order to see it.

11. Only yellow light is reflected
Seeing color
The color an object appears depends on the colors of light it reflects.
For example, a yellow book only reflects yellow light:
Homework
White
light
Only yellow light is reflected

12. A pair of blue pants would reflect only blue light to the eyes.
Blue Light reflected to eyes
White
light
When a person sees white, all the colors of the spectrum are being reflected off the object back to the eye. A white hat would reflect all seven colors.
All colors reflected to the eyes
White
light

13. Using coloured light
When a person sees black, all the colors of the spectrum are being absorbed by the object. There’s no reflection of color back to the eye so the object looks black.
Shirt looks black. No light is reflected to the eyes.
White
light

14. Now you try
Determine how you see the colors of the following objects: