Program of Studies investigate light beams and optical devices, and identify phenomena that provide evidence of the nature of light (e.g., evidence provided by viewing the passage of light through dusty air or cloudy water) measure and predict angles of reflection investigate, measure and describe the refraction of light through different materials (e.g., measure differences in light refraction through pure water, salt water and different oils)

Unit C: Light and Optical Systems Reflection Refraction Total internal reflection Telescopes

Light travels in straight lines only

Shadows How do we know? We have a clear shadow. Shadows form because light does not go around corners, so we can “block” light rays with opaque materials

Light travels in straight lines The closer the object is to the light source, the more light is blocked, and a larger shadow is formed.

Light Travels in Straight lines

Reflection + Refraction

Reflection vs. Refraction Material Shiny Change in density What happens? Light bounces Light bends Technology Mirrors Lenses

Reflection

Reflection Incident ray <i: Reflected ray <r: Normal Beam of light going towards the reflective surface Reflected ray <r: Beam of light coming off the reflective surface Normal An imaginary line that runs perpendicular (at 90o) to the reflective surface. Angle of incidence <i : Incoming ray of light (from source) Angle of reflection <r : Reflected ray

Reflection

The normal The angle of incidence and angle of reflection are measured from the normal!

Reflection

Infinite reflection

Reflection

The Law of Reflection First discovered by… Euclid <i = <r The angle of incidence equals The angle of reflection

The law of reflection

Total Internal Reflection

Total internal reflection But how can you “pour” laser light into your hand? Light will reach a critical angle, and then reflect rather than refract

Total internal reflection This is the principle behind fibre optics

Lab Do lab activity on reflection pg 195 science in action, full lab write up

Refraction As light passes from one material to another material, it speeds up or slows down This causes the beam of light to bend, making objects appear broken, or in another place

Refraction

Refraction Incident ray <i: Refracted ray <r: Normal Beam of light going towards the refractive surface Refracted ray <r: Beam of light coming from the refractive surface Normal An imaginary line that runs perpendicular (at 90o) to the refractive surface.

Refraction

Refraction-densities As light goes from an object that is more dense to less dense (ex. From water to air) light bends away from the normal As light goes from an object that is less dense to more dense (ex. From air to water) light bends towards the normal

Refraction

Refractive Index (Density) Material Refractive Index Air 1.0003 Water 1.33 Glycerin 1.47 Immersion Oil 1.515 Glass 1.52 Diamond 2.42

Did someone say diamond?

Refraction makes it sparkly

Refraction-prisms…..Newton

Refraction-lens in eye….Al

Reflection vs. Refraction

Telescopes

Light bends (refracts) through glass objective lenses Types of Telescopes! Three Basic Types Refracting Combination Light bends (refracts) through glass objective lenses Uses the best of both! Reflecting Mirrors reflect images to eyepiece. Focuses colors better: Newton’s Telescope

Do Lab Refraction pg 202