Producing Visible Light

EQ: How is visible light produced?

Vocabulary

• Illuminate – to see an object because of reflected light

• Luminous Object – an object that gives off its own light– i.e. light bulb, burning match, sun

EQ: How is visible light produced?

Vocabulary

• Incandescence – production of light by materials at a high temperature

• Sun gives us the most of the visible light in our world

Spectroscope – an instrument that tells you what colors of light are produced by each bulb

EQ: How is visible light produced?

Incandescent light

• Produce light when a filament inside the bulb gets hot

Tungsten

filament

1. Electric current passes through the filament and heats it up

2. When it gets hot enough, it gives off a red light, which gives off low frequencies

3. As it gets hotter, the filament gives off waves with higher frequencies.

4. Once it gets hot enough to give off violet light, all frequencies combine to give off white light

EQ: How is visible light produced?

Incandescent light

• Most like the sun –Gives off all the colors of visible

light

–Gives off heat.

FYI- Not very efficient. Most of the energy given off is infrared rays. (that’s why your light bulb gets hot)

EQ: How is visible light produced?

Fluorescent Light

• Glass tube that contains a gas and is coated on the inside with powder

• When an electric current passes through a fluorescent bulb causes the gas to emitultraviolet rays. • Next the UV rays hit the

powder coating and the coating emits light

Fluorescent Light Bulb

EQ: How is visible light produced?

Fluorescent lights

• Fluorescent lights give off most of their energy as light

• Usually lasts longer than incandescent bulbs and uses less electricity

EQ: How is visible light produced?

Luminescence

• Production of light without the high temperatures needed for incandescence

Bioluminescence

• Light energy that occurs as a result of a chemical reaction among proteins and oxygen in an organism– Examples – firefly, jellyfish

EQ: How is visible light produced?

Class Work and Homework

• Fill In– What did I learn– Confused– Say

Read Pages 88 – 92, questions 1-6

EQ: How is visible light produced?