1. 5.1 Light in Everyday Life Our goals for learning
How do we experience light?
How do light and matter interact?

2. Light is the ONLY thing you see
Light is the ONLY thing you see! All visible objects either emit or reflect light.

3. How do we experience light?
The warmth of sunlight tells us that light is a form of energy
The flow of energy in light is measured in watts (like a light bulb)
1 watt = 1 joule/s

4. The Color Spectrum
When sunlight passes through a prism, it separates into a spectrum of all the colors of the rainbow.

5. The Color Spectrum
Sunlight is an example of what is called white light. White light is a combination of all the colors.
Under white light, white objects appear white and colored objects appear in their individual colors.

6. The primary colors of light are red, blue and green
They can add to produce all other colors
Black is the absence of color

7. Ways light and matter interact:
Matter can emit light: Ex: A heated solid, liquid or gas under high pressure

8. Ways light and matter interact:
Almost everything we see is made visible by the light it reflects.

9. Reflection Light can be evenly reflected from a surface like a mirror
The laser light is reflected off a mirror

10. Scattering Light can also be reflected from rough surfaces
The laser light is being reflected from a mineral

11. Scattering

12. Scattering

13. Reflection and Scattering
Mirror reflects light in a particular direction
Movie screen scatters light in all directions

14. The light always obeys the Law of Reflection
Angle of incidence = angle of reflection

15. Ways light and matter interact:
Transparent materials, such as air, water, or window glass, allow light to pass through and we can see objects clearly
Translucent materials, like stained glass, also transmits light but objects can’t be seen clearly.

16. Transparent Materials
The atoms in the material absorb the energy and immediately reemit it as light.
Ex. Glass and water
The color of a transparent object is the color of the light it transmits.

17. Color by Transmission
For example, blue glass transmits only energy of the frequency of blue light; energy of the other frequencies is absorbed and warms the glass.

18. Ways light and matter interact:
Opaque materials, such as thin paper or frosted glass, allow the passage of light in diffused directions so that we can’t see objects through them.

19. Objects can be transparent for some light and opaque for other light
Objects can be transparent for some light and opaque for other light. For example, infrared can see through some things that are opaque in visible light

20. …And some things transparent in visible light are opaque in infrared
Lots more “infrared world” photos online!

21. Interactions of Light with Matter
Interactions between light and matter determine the appearance of everything around us

22. The color of an object depends on both the colors of light it absorbs and the colors of light it reflects.

23. Thought Question Why is a rose red?
The rose absorbs red light.
The rose transmits red light.
The rose emits red light.
The rose reflects red light.

24. Thought Question Why is a rose red?
The rose absorbs red light.
The rose transmits red light.
The rose emits red light.
The rose reflects red light.

25. Summary How do we experience light? Light is a form of energy
Light comes in many colors that combine to form white light.
How does light interact with matter?
Matter can emit light, absorb light, transmit light, and reflect (or scatter) light.
Interactions between light and matter determine the appearance of everything we see.