Physics

Physics

Light is an electromagnetic wave it travels very fast (3.0. X 10 8 m/s) 300 000 000

The electromagnetic spectrum is organized in order from the longest wavelength/lowest amount of energy to the shortest wavelength and highest amount of energy.

 The sources of light are…

  • Bioluminescence: Emission of light by a living organism (fireflies)

  • Chemiluminescence: The production of light from chemicals (glow sticks)

  • Luminescence: Emission of light from materials that are relatively cool.

  • Fluorescence: production of visible light by an object that has absorbed ultraviolet light. (Highlighters & fluorescent light bulbs)

  • Phosphorescence: When a special material phosphors absorb UV light and emit that light over a period of time. (Glow in the dark items)

  • Incandescence: The production of light energy when an object is heated to a high temperature. (Regular light bulbs and flame)

  • Triboluminescence: When two crystals are rubbed or crushed together and emit light. (two sugar cubes rubbed together & two quarts stones rubbed together)

  • Electric discharge: an electric current passes through gas, causing gas to flow. The electricity causes the gas to glow. (Lighting & neon lights)

  • Light emitting Diode (LED) : An electronic device that allows an electric currents to flow in only one direction using semiconductors (silicon), are energy, efficient, and produce less heat (LED Christmas lights)

Transparent materials , lets lights pass through it easily

Translucent materials let some light pass through it

Opaque material does not let any light pass through it

Laws of reflection

  1. The angle of incidence must equal to the angle of reflection

  2. The incident ray, reflected ray & the normal all lie in the same plane.

Images are described using SALT

1.Size (is the image bigger or smaller than the object)

2. Attitude (is the image upright or inverted)

3. Location ( is the image located in front of or behind the mirror (real) or behind the mirror (virtual)?

4. Type: Is the image virtual or real?

Refraction: 

Refraction is the bending of light as it travels from medium to another medium of different density. 

Light changes its speed when it travels through different media.

There are two rules of refraction…

  1. The incident ray, refracted ray and the normal all lie in the same plane. 

  2. If a light ray travels from a fast -> slow medium it bends toward the normal, but if it travels from a slow -> fast medium it bends away from the normal

Partial refraction occurs when light passes through a boundary between two different materials and bends as it enters the new material

The index of refraction is a quantitative physical property that can distinguish the different types of media,

The index of refraction is the speed of light in a vacuum\the speed of light in a medium. 

Total internal reflection:

When light travels from a slow to fast medium, light bends away from the normal. It speeds up at the boundary between the media it is travelling through.

There are two conditions for total internal reflection..

  1. Light has to travel from a slow to fast medium 

  2. The incident ray has to be greater than the critical angle so no refraction occurs. 

Cameras and Binoculars

Cameras and binoculars use glass prisms that have a high index of refraction and place

them in a particular angle within a device in order to reflect 100 % of the light internal.

Critical Angle

  • When the refracted ray is = to 90 degrees, the incident ray this occurs at is referred to as the critical angle

  • If the angle of incidence increases beyond the critical angle, the refracted ray will be reflected back into the media and the refracted ray will then disappear and only the reflected ray will be visible in the medium