Grade 10 Academic Science Light and Optics Unit

Unit Organization Light and Optics Production and Reflection Refraction Lenses and Optical Devices

Light is Weird Light is a form of energy visible to the human eye Light does not need a medium to travel Light sometimes displays properties of waves and sometimes displays properties of particles Light travels at 300 000 000 m/s Light takes 8.3 minutes to reach the Earth Light travels in straight lines if travelling in the same medium Life on Earth would not exist without light

The Electromagnetic Spectrum An electromagnetic wave is a wave that has both electric and magnetic parts, does not require a medium, and travels at the speed of light There are many different types of electromagnetic waves - i.e. x-rays, microwaves, radio waves Visible light is an electromagnetic wave that the human eye can detect Visible spectrum of colours: red, orange, yellow, green, blue, indigo, violet Refer to page 466 in your textbook for more examples of the electromagnetic spectrum

Visible Light and the Spectrum White light is composed of all the colours of the rainbow. ROYGBIV red-orange-yellow-green-blue-indigo-violet A glass prism is capable of separating the colours because each colour travels through the prism at a slightly different speed.

Why we see things! We see things because light hits our eyes from all objects. Luminous Something that provides it’s own light i.e. sun or lightbulb Non-luminous Something that reflects or absorbs light i.e. moon, mirror

Sources of Light - Natural Sunlight (solar radiation) Stars (burning balls of gas) Lightning Core of the Earth (magma) Bioluminescent objects

Sources of Light – Electric Powered Incandescent lights Emitting light because of high temperature Light emitting diodes (LED’s) Electric Discharge Use of electricity to excite a gas Fluorescent Lights filled with mercury vapour

Sources of Light - Combustion Candles Fire Oil lamps

Sources of Light - Chemical Chemiluminescence Light produced by a chemical reaction i.e. glow sticks Bioluminescence Light produced by a living thing i.e. fireflies, glow worms, plankton, fish, jellyfish Phosphorescence Light produced for some time after receiving energy from another source i.e. hands on a watch Fluorescence Light produced while receiving energy from another source i.e. black light

Incandescent Light Electricity passes through a filament, causing it be become hot and give off light

Light Emitting Diodes (LED’s)

Electric Discharge Electricity causes the gas to glow E.g. neon sign

Fluorescent Light Fluorescent light filled with mercury vapour current + mercury = UV light UV light absorbed by fluorescent coating on inner surface of tube

Black light

Watch

Plankton

Glowsticks

Firefly

Glow worms

Deep-Sea Fish