A billowing tower of gas and dust rises from the stellar nursery known as the Eagle Nebula. This small piece of the Eagle Nebula is 57 trillion miles long (91.7 trillion km)

Optics

The Crab Nebula is a supernova remnant, all that remains of a tremendous stellar explosion. Observers in China and Japan recorded the supernova nearly 1,000 years ago, in 1054

Intricate structures of concentric gas shells, jets of high-speed gas and shock-induced knots of gas make up this complicated planetary nebula. The Cat's Eye Nebula is about 1,000 years old, and could have resulted from a double-star system

Hubble Space Telescope

And from the very large…

Amoeba

Paramecium

H1N1 Influenza virus (approx 100nm)

4.1 Producing Light Light is emitted from matter by electrons that have absorbed energy to become ‘excited’, then the electrons release back some of the extra energy as light.

Light Emission Source of Energy Absorbed Sunlight Nuclear fusion which produces enough heat to excite electrons

Source of Energy Absorbed Light Emission Source of Energy Absorbed Incandescence eg. Light bulb with a filament Electricity which makes the filament hot enough to excite electrons – unfortunately only 5% efficient.

Eg. LED lights & neon signs Light Emission Source of Energy Absorbed Electric Discharge Eg. LED lights & neon signs Electricity which directly excites the electrons

Source of Energy Absorbed Light Emission Source of Energy Absorbed Fluorescence eg. fluorescent bulbs Electricity that excites the electrons to emit UV radiation, which in turn excites the electrons in the white powder coating inside the bulbs.

Source of Energy Absorbed Light Emission Source of Energy Absorbed Phosphorescence eg. Glow in the dark stickers UV radiation excites electrons that slowly release their energy, which gives its longer-lasting effects

Light Emission Source of Energy Absorbed Chemiluminescence eg. Glow sticks Chemical reactions in which electrons of the products release energy.

Source of Energy Absorbed Light Emission Source of Energy Absorbed Bioluminescence eg. fireflies Like chemiluminescence, but reactions in living cells