1. LIGHT

2. What is LIGHT? A type of electromagnetic wave
Type of energy that travels as a wave
NO medium is required
We see things because light reflects off of them

3. What is an Electromagnetic Wave?
A transverse wave
A wave that can travel through space or matter and consists of changing electric and magnetic fields.
Field-a region around an object that can exert a force without actually touching the object
Example:magnet
Waves are produced by the vibration and movement of an electron

4. How are Electromagnetic Waves Produced?
Produced by the vibration and movement of an electron
When an electron changes energy levels, energy is emitted
The energy is emitted as a particle called a photon
A stream of photons carries the energy from the electron, as a light wave.
photon

5. The Electromagnetic Spectrum

6. Visible Light We see different wavelengths as different colors
When all colors are combined, we see white light
When there are no colors, we see black

7. Visible Light Light travels in a straight line
When shining a light, closer objects appear brighter, this appears for 3 reasons
The beam of light spreads out
Absorption
Scattering

8. Absorption & Scattering
the air particles around the light absorbs (takes) some of the energy from the light
Scattering
Light scatters in all directions
The particles that absorb energy (around the light source) give off light energy
This makes us able to see things near the light that are not on the line that the light is traveling
Shorter wavelengths scatter more light than longer wavelengths.

9. Law of Reflection Law states that:
angle of incidence = angle of reflection
Angle of Light going into surface = angle going out
If the reflecting surface is smooth, then light reflects off of all points at the same angle.
If the reflecting surface is rough, then light reflects off at many different angles.

10. LIGHT & COLOR Light can interact with matter in 3 ways TYPES OF MATTER
Reflected-light rays reflect at angle of incidence
Absorbed-energy is transferred to the particles
Transmitted- light passes through the matter
TYPES OF MATTER
Transparent-light is easily transmitted
Translucent-transmits and scatters light
Opaque-does not transmit any light

11. COLORS of OBJECTS
The color of an object is determined by the wavelength of color that reaches your eye.
OPAQUE OBJECTS
When white light hits a colored object, some colors are absorbed and some are reflected
Only the light that is reflected reaches your eyes, this is the color that we see
White objects REFLECT ALL colors
Black objects ABSORB ALL colors
TRANSPARENT OBJECTS
We see the color that is transmitted through the matter

12. MIRRORS----- Images in mirrors are reversed left to right
Light waves travel in straight lines in all directions from a light source
An arrow called a ray can represent the path and direction of the light wave
These rays are used to show the light after it is reflected or refracted- it shows the change of direction

13. Mirrors Reflect Light Mirrors are classified by their shape,
plane, concave, and convex
The shape of the mirror affects the way light reflects from it and how an image appears

14. Plane Mirrors A mirror with a flat surface
When you look at it, your reflection is upright and the same size as you are
Images are reversed from left to right
Image appears to be the same distance from the mirror as in front of it
Mirrors are opaque, light does NOT travel through them
The image created is virtual-your brain sees the reflected light and thinks it is straight behind the mirror

15. Plane Mirrors

16. Concave Mirrors Mirrors that are curved inward Form virtual images
Can form REAL images-image though which light actually passes, can be projected onto a screen
Create a ray diagram to decide if an image is real or virtual

17. Ray Diagram Terms

18. How to Draw Ray Diagrams
Draw a ray from the top of the object parallel to the axis. It will reflect and go straight through the focal point.
If the distance between the object and the mirror is more than one focal length, draw a ray from the top of the object through the focal point. The ray will reflect parallel to the axis.
If the object is less than one focal length away from the mirror, draw a ray though the top of the object from the focal point and it will reflect parallel to the axis.

19. Virtual or REAL?
Draw a ray diagram to answer the question, you need to draw two rays from the top of the object
If the reflected rays cross in front, of the mirror, a REAL image is formed
The crossing point is the top of the image
If the reflected rays do NOT cross, trace the reflected rays in straight lines behind the mirror
These lines will cross to show where the image forms
This is a VIRTUAL image
If the object is placed at the focal point of a concave mirror, NO IMAGE IS FORMED

20. REAL IMAGE

21. VIRTUAL IMAGE

22. CONVEX MIRRORS A mirror that curves out toward you
All images formed are VIRTUAL and UPRIGHT and SMALLER than the original

23. Refraction
The bending of a wave as it passes at an angle from one medium to another.
This occurs because the speed of light changes according to the medium
When a wave enters a new medium at an angle, the part of the wave that enters first begins to travel at a different speed from the rest of the wave.

24. Refraction and COLORS
White light is made up of all colors of visible light
Each color has its own wavelength
When white light is refracted, the amount that the light bends, depends on the wavelength.
Light waves with SHORT wavelengths bend MORE
This allows white light to be separated into different colors during refraction
This is why and how rainbows form

25. Diffraction The bending of waves around barriers or through openings
Greatest amount of diffraction occurs when the opening is the same size as the wavelength or smaller
Light waves cannot diffract around large obstacles
This is why you can’t see around corners
Light waves always diffract a small amount

26. Interference When two or more waves overlap
Constructive Interference
Resulting wave has a greater amplitude-bright spots of light
Destructive Interference
Resulting wave has a smaller amplitude-dark spots or dim light.

27. Mixing COLORS of Light
RED, BLUE and GREEN can be combined in different ratios to produce all colors of visible light
Called the Primary Colors
When they are mixed, they make secondary colors
Mixing Colors of Pigment
Pigment-material that gives a substance color by absorbing colors of light and reflecting others
This is why we cannot mix red, blue and green paint to make white paint.

28. Lenses Refract Light
Lens- a curved, transparent object that forms an image by refracting, or bending light
Classified by shape
Convex-thicker in the middle than at the edges
Concave-Thinner in the middle than at the edges

29. Convex Lenses Light is refracted towards the center
Light rays enter parallel to axis and are refracted so that they go through the focus point
Amount of refraction and focal length depends on the thickness of the lens
Light rays passing through the center of a lens are not refracted
Can form REAL AND VIRTUAL images, depends on the focus length and placement of the object

30. CONVEX LENSES

31. Concave Lenses
Light rays enter parallel to the axis and bend away from each other toward the edges of the lens
The rays never meet
Always form a VIRTUAL image