Optics+Course

= OPTICS = //Lesson notes - Grade 10 Optics - SNC2D1 - Ontario Curriculum 2009//

**Optics:**

 * The branch of physics that deals with light

Models of light:

 * Geometric model - William Snell XVI century
 * Wave model - J.C. Maxwell XIX century
 * Photon model - Max Planck XX century

Comparison of the three models

(To be added)

Sources of Light:

 * Direct light: Luminous objects that produce their own light
 * Indirect light:Non-luminous objects do not produce their own light, they reflect a luminous objects light

Types of light

 * **Incandescent light:** When materials are heated light is produced this form of light is called incandescent light
 * Sunlight
 * Light bulb
 * Molten metals
 * **Phosphorescent light:** Certain materials called phosphors gain energy from the surroundings and emit the extra energy that it has absorbed. The glow lasts for several hours.
 * Luminous dials of certain watches and clocks are examples
 * **Fluorescent light:** Materials that emit light only during the time it receives energy from another source.
 * Neon lamps
 * Fluorescent light bulbs (These are four times more efficient as an incandescent bulb) It has an efficiency of 20%

Interaction of light with matter - Types of materials

 * **Transparent:** Materials that allow light to pass through, examples are water, clear plastic, glass etc.
 * **Translucent:** Materials that allow some light to pass through them, some light is scattered, examples are frosted glass, stained glass, shower curtain materials etc.
 * **Opaque:** Materials that do not allow light to pass through them, examples are wood, stone, rock etc.

Characteristics of Light
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 * **Rectilinear propagation:** Light appears to travel in straight lines through a uniform medium (uniform temperature and humidity if air is the medium)
 * Proof that light travels in straight lines
 * Creation of shadows (umbra and penumbra)
 * Creation of upside images
 * Types of shadows created
 * Umbra: When a point source light falls on an object and creates a shadow the region where light cannot reach is called the umbra and it is a distinct region
 * Penumbra: When a large source of light falls on an object it creates two types of shadow one that is distinct like the umbra and the second type of shadow that is a mixture - some light falls on this shadow, this region is called penumbra
 * Types of Images:
 * Real image: Images that can be projected on to a screen (Light comes directly from this image)
 * Virtual image: Images that cannot be projected on to a screen (Light does not come from this kind of image)
 * Characteristics of an image:
 * Real or Virtual - Kind of image
 * Erect or Inverted - Attitude of the image
 * Enlarged, Same size or Diminished - Magnification

Reflection Terminology

 * **Ray:** A directed straight line representing the path followed by the light
 * **Beam:** A bundle or rays
 * Types of Beams
 * Parallel beams
 * Converging beams
 * Diverging beams
 * Incident ray: Ray of light approaching the reflecting surface
 * The ray of light leaving th reflecting surface
 * Point of incidence: Point on the mirror where the incident ray strikes the reflecting surface
 * Normal (N): A line perpendicular to the reflecting surface at the point of incidence
 * Angle of incidence (//i// ) Angle between the incident ray and the normal
 * Angle of reflection (//r// )Angle between the reflected ray and normal
 * **Laws of reflection:**
 * The angle of incidence is equal to the angle of reflection
 * The incident ray reflected ray and the normal all lie in the same plane

You tube clip laws of reflection media type="youtube" key="qKiMGBT1JQc" width="425" height="350"

media type="youtube" key="SCgrQIPx_3E" height="390" width="640" Image of reflection of light from a plane mirror from external site []

Pin hole camera image from []

Curved Mirrors
Link to simulation

media type="youtube" key="UQrKtiKfmMU" width="425" height="350"


 * **Concave - Converging mirror**
 * **Convex - Diverging mirror**
 * Related terminology
 * C - Center of curvature ( = 2f)
 * F - Principal focus (f = focal length)
 * V - Vertex
 * R - Radius of curvature
 * PA - Principal axis
 * **Ray diagrams** - Properties of reflected rays with respect to its path
 * An incident ray parallel to the principal axis is always reflected through the focus
 * An incident ray passing through F is always reflected parallel to the principal axis
 * An incident ray passing through the center of curvature is always reflected back
 * An incident ray striking the vertex is reflected based on the laws of reflection (angle of incidence = angle or reflection)

The following is a link to characteristic and position of image after reflection

The image is from http://www.tutorvista.com/search/real-images-vs-virtual-images Concave mirrors

media type="youtube" key="YjFB6je1T9g" width="425" height="350"

Ray diagram concave mirror - Image formation from http://cr4.globalspec.com/PostImages/200712/Concave_Mirror_D3115558-A803-447A-34D41428022BD49E.jpg

Convex mirror media type="youtube" key="tlLeW1B9v4E" width="425" height="350"

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