1. A Brief Look at
LIGHT

2. Light is
a form of electromagnetic radiation that is detectable by the eye…
but we can’t see it!!!

3. The Speed of Light in air is about 300 000 000 m/s. It’s fast!
depends on the material the light is travelling through.
is the fastest possible speed for any object???

4. Diagrams with Light are referred to as ray diagrams
where a ray is a single path followed by light
and a beam is a ‘bundle’ of light rays.

5. When light strikes matter
It can be affected in 3 different ways:
Transmitted: light passes through a medium
Ex. Windows
Reflected: light bounces off an object
Ex. Mirrors
Absorbed: light disappears (or certain wavelengths)
Green object  all wavelengths of light except green are absorbed

6. Classifying Objects
Objects may be classified based on how well they transmit light:
Transparent: transmits ALL light
Opaque : transmits NO light
Translucent: transmits SOME light

7. Electromagnetic Spectrum
Light travels as an Electromagnetic wave which is made up of particles of energy called photons.
Electromagnetic waves are made up of electrical energy and magnetic energy
Wavelength: the distance between peaks on a wave

8. Electromagnetic Spectrum
There are many types of electromagnetic waves. The main difference between them is their wavelength
Electromagnetic Spectrum represents different types of waves arranged according to their wavelength

9. Electromagnetic Spectrum p.409 text

10. Electromagnetic Spectrum Uses

11. Break:
Watch Eureka video

12. The Reflection of Light
Regular Reflection: this is reflection of light from smooth shiny surfaces.
The next slide diagram shows how light behaves during regular reflection.

13. Laws of Reflection Normal Incident Ray Angle of Incidence
Angle of Reflection
Reflected Ray
90o
Mirror
Point of incidence/ axis

14. Laws of Reflection
First Law: The angle of incidence is equal to the angle of reflection
Normal
Incident Ray
Angle of Incidence
Angle of Reflection
Reflected Ray
Mirror

15. Laws of Reflection Laws of Reflection
Second Law: The incident ray, reflected ray, and normal all lie on the same plane
Normal
Incident Ray
Angle of Incidence
Angle of Reflection
Reflected Ray
Mirror

16. Diffuse Reflection
Many surfaces appear to be smooth, however when they are viewed under a microscope it is clear they are not.
Because of the uneven surface, the light rays are scattered in many directions (diffused).

17. Diffuse Reflection
Further examination of a irregular surface show that they too obey the laws of reflection (ie. Angle of incidence = angle of reflection).

18. Diffuse Reflection
Most objects are made of rough surfaces (and therefore scatter light); if this did not happen, indoor lighting would not be effective.
ie. Walls, floors, ceilings, etc. scatter light in all directions, making them visible.

19. Optical Images
An image is the representation of an object formed by the interaction of light rays.

20. Optical Images
An image is the representation of an object formed by the interaction of light rays.
Characteristics: Size: same size, bigger or smaller than object
Attitude: image is upright, flipped or laterally inverted
Location: behind the mirror or in front of the miror the same distance as the object
Type : virtual or real

21. Images Formed in Plane Mirrors
How do I see an image of the arrow??

22. Images Formed in Plane Mirrors
Light from the arrow hits the mirror

23. Images Formed in Plane Mirrors
..and is reflected into my eye

24. Images Formed in Plane Mirrors
The image!!
..and my brain ‘sees’ the image where the light appears to have come from!

25. Characteristics of a PLANE MIRROR Image
Size: same size as object
Attitude: image is upright, and laterally inverted
Location: behind the mirror the same distance from the mirror as the object
Type : virtual