Part 2: Behaviors of Light

Speed of light In a vacuum, the speed of light is 300,000,000 m/s Light travels slower as the medium gets denser. Example: Light will travel slower in water than in air. When light changes mediums, the speed and wavelength change. Frequency remains the same.

Light travels in straight lines Light will travel in a straight line until it strikes a surface Laser

Luminous and non-luminous objects A luminous object is one that produces light. A non-luminous object is one that reflects light. Luminous objects Reflectors -Light Bulbs -The Sun -Computer Screens -The moon -Your Shirt - Paper

Reflection The color an object appears depends on the colors of light it reflects. Reflection occurs any time all or part of a light waves bounces back from a surface. Homework White light Only red light is reflected For example, a red book only reflects red light:

White Light White light is not a single color; it is made up of a mixture of the seven colors of the rainbow. We can demonstrate this by refracting white light with a prism: This is how rainbows are formed: sunlight is “split up” by raindrops.

The colors of the rainbow: Red Orange Yellow Green Blue Indigo Violet

The Normal The normal is an imaginary line from which angles are measured. It is always drawn perpendicular to the surface of the medium.

Frequency remains the same Refraction The bending of a wave when it passes at an angle from one medium to another medium Remember: waves travel at different speeds through different substances. Frequency remains the same

If angle of incidence = 0, no refraction takes place

Refraction Wave that goes from higher velocity to lower velocity bends toward normal Faster medium = greater angle Slower medium= smaller angle Measured from normal

Refraction Wave that goes from lower velocity to higher velocity bends away from normal

Refraction For the following diagrams draw (1) the normal, (2) the direction of the wave if it did not bend, and (3) the direction of the wave if it did bend. Өr Өi Өi Өr Өr Өi Normal Өi Өr Straight line path

Refraction

Reflection: Reflection is when waves bounce off the surface of a medium. Light reflects differently off a smooth surface than off a rough surface as shown below.

Reflections Specular reflection Smooth surfaces Reflected light remains organized

Reflections Diffuse reflection Rough surfaces Reflected light scatters

Angle of Incidence = Angle of Reflection The Law of Reflection: Angle of Incidence = Angle of Reflection Өi = Өr mirror normal Reflected ray Incident ray өi өr

Constructive vs. Destructive Interference When light waves interfere with each other, they effect the intensity (or brightness) of the light Constructive: causes the light to get brighter Destructive: causes the light to get dimmer

Diffraction Refers to the spreading or bending of waves around edges. With light this causes interference patterns to be created. Experiments called the single-slit and double-slit are used to show the interference patterns.

Single and Double Slit Experiments The brighter areas are caused by constructive interference and the darker areas are caused by destructive interference.

Polarization Light waves occur in many orientations and on multiple planes. We can use polarizers to filter out directions we don’t want.

Polarization By polarizing the light, we can change how the light looks and how much light can pass through a surface Examples: