1. Light

2. Some basic information on light
Light is the fastest thing in the universe. It moves at…
m/s
Other speeds in m/s: Sound: 343 m/s
Car on highway: 28 m/s
You running: 7.5 m/s

3. Light versus sound
Explain why you see lightning before you hear thunder during a thunderstorm.

4. Light versus sound
Why do you see a firework explode before you hear the explosion?

5. What is a lightyear?
This is a unit of distance. It tells us how far light can travel in one year.
This is very useful for measuring extremely long distances because light travels VERY fast and a year is a LONG time!
1 lightyear = m

6. Light
Light is a form of energy, meaning that it has the ability to do work.
Light travels in waves, which propagate in a straight line.

7. Anatomy of a wave

8. Definitions: Crest: The top parts of a wave.
Trough: The low points of a wave.
Amplitude: The height of a wave from its rest position In light, this is its brightness.

9. Definitions
Wavelength: The distance between any two adjacent crests (or troughs). In light, this affects its colour.

10. Definitions
Frequency: This the number of crests (or troughs) that pass by in 1 second. It is measured in “cycles per second”, or Hertz (Hz).
If you see 100 crests in 25 seconds, what’s the frequency? ___
500 crests in 2.5 seconds, what’s the frequency:

11. For light waves, the wavelengths are small
These wavelengths are so small that they’re usually measured in nanometers (1 nm = m)
The colours we can see are:
Red nm
Orange 600 nm
Yellow 580 nm
Green 540 nm
Blue nm
Indigo 450 nm
Violet 425 nm

12. Electromagnetic spectrum

13. Some non-visible radiation
Longer wavelength Shorter wavelength
Radio Micro- Infrared Visible UV X-rays Gamma waves waves rays light rays rays

14. Different wavelengths:
The shorter the wavelength, the more energy the wave carries. But it can’t travel far.
The longer the wavelength, the less energy the wave carries. But it can travel further.

15. Electromagnetic waves
Electromagnetic waves (light, X-rays, microwaves, etc) do not need a medium (material) to travel through.
Other waves do need a medium:
Water waves require water as a medium.
Sound waved require air as a medium.

16. Greenhouse Effect

17. White Light
White light is made up of all the colours. We can separate it into its colours by using a prism:

18. White light
We don’t see objects… we see light reflecting off objects. Different objects reflect specific wavelengths of light.
All other wavelengths of light are absorbed.

20. White and Black White objects reflect all wavelengths of light.
Black objects absorb all wavelengths of light

22. Should you wear white or black?

23. Fill in your table (TRANSPARENT)
What happens when light strikes a transparent material?
Examples of materials:

24. Fill in your table (TRANSLUCENT)
What happens when light strikes a translucent material?
Examples of materials:

25. Fill in your table (OPAQUE)
What happens when light strikes an opaque material?
Examples of materials:

26. Drawing Cloud Yellow traffic light White car Black tire
Clear glass window

27. Angle of Incidence and Reflection
The normal is an imaginary line that is perpendicular to the surface.
The angle of incidence is the angle the ray of light makes with the normal. It is the same as the angle of reflection.

28. When light reflects off an object (such as a mirror), it bounces back at the exact same angle that it hit.

29. Refraction
When light passes through a different medium, it can be bent. This is called refraction.
The angle of incidence is smaller the same as the angle of refraction.

30. Refraction

31. Different mediums change the angle of light.

32. What happens when you put light through a convex lens?

33. What happens when you put light through a convex lens?

34. What happens when you put light through a convex lens?

35. What happens when you put light through a concave lens?

36. What happens when you put light through a concave lens?

37. What happens when you put light through a concave lens?

38. Your eye works the same way

39. How your eyes work

40. How your eyes work

41. Review Question
What is the focal point of a lens?

42. How your eyes work

43. How your eyes work

44. Myopia (focal point before retina)

45. Myopia (focal point before retina)

46. Hyperopia (focal point after retina)

47. Hyperopia (focal point after retina)