Unit 3 – Light and Optic Systems

Topic 5 - Extending Human Vision

Telescopes: help us to see distant objects

Two main types of telescopes:

Refracting: uses an eyepiece and objective lens (viewed straight on)

Reflecting: uses an eyepiece and objective mirror (viewed through the side)

Binoculars: two reflecting telescopes mounted side by side, prisms reflect the light to the eyepiece.

Topic 6 – The Source of Colours

Newton discovered that white light is made up of different colors of light.

When white light is refracted into its different colors the resulting pattern is called a spectrum.

For sunlight the colors are red, orange, yellow, green, blue, indigo, and violet. (ROY G. BIV) this is called a solar spectrum.

When we see a color what we are really seeing is the absence of other colors. E.g. A blue bottle absorbs all the other colors except blue, therefore we see blue.

Additive primary colors: they are red, green, and blue. They are called this because when you add all three together in the proper amounts they will make white light.

Secondary Colors: yellow, cyan, and magenta. Produced when, the light from two primary colors are combined.

There are two types of cells in the human retina:

Rods: tiny cylinders that detect the presence of light

Cones: detect colour, there are three types of cones, and each type responds to a different colour.

Colour blindness: occurs when the cones don’t detect colours properly.

Topic 7 – The Wave Model of Light

Is light a particle or a wave?

Waves consist of crests and troughs

Crest: the peak or high part

Trough: the bottom or low point

Wavelength: the distance from crest to crest or trough to trough.

Amplitude: the height of the crest or the depth of the trough

Frequency: the number of cycles completed by a vibrating object per unit of time. Usually measured in Hertz (Hz)

Laser: Light Amplification by the Stimulated Emission of Radiation

Incoherent light: crests from one wave might interrupt a trough from another jumbling them up. (Incandescent light bulb)

Coherent: light emits waves with only one frequency and wavelength causing them to work together (laser)

Many uses include:

-Eye surgery

-Scanning merchandise at a store

-Laser guided missiles

-Blue Ray

Topic 8 - Beyond Light

Visible light and all other invisible forms of electromagnetic energy exist on the electromagnetic spectrum.

Know figure 3.62 on page 249

Infrared radiation: heat radiation, anything that emits more heat than its surroundings. (Used on cops)

Radio waves: longer wavelength than infrared and there are many kinds. ex. Microwaves

Ultraviolet radiation: (UV) very energetic radiation, causes damage to skin and eyes. Increased problem as a result of depletion of the Ozone layer.

X rays- pass through tissues like skin and muscle but are absorbed by bone

Gamma Rays- has the ability to destroy cells, can be used in cancer treatment.