What is Light Energy?

What is Light Energy?

Sources of Light

• Light can be found almost everywhere.

• We can see certain objects because they are light sources.

• They produce their own light

• However, most objects do not produce any light, such as... tables, chairs, and flowers.

• We can see them when a light source is available.

• Humans discovered long ago that they could make their own light.

• The discovery of fire changed how people lived.

• Humans invented many artificial sources of light. For example: the flashlight

• In the 1900s inventions brought electrical energy into homes and businesses.

• Electrical energy can change into light energy.

• With light sources such as lightbulbs, you can still do work after the sun sets.

• Your power likely comes from a power plant.

• The power plant might use coal, gas or even wind to make electrical energy.

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Light Waves we See

• The form of light energy that we can see is called visible light.

• Light energy travels from its source as waves.

• Light waves have wavelengths and frequencies.

• Wavelength is the distance between a point on one wave and a similar point on the next wave.

• The frequency of a wave is the number of waves that pass a point in a certain amount of time.

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• White light such as light from a lamp or the sun is actually a blend of colors.

• The colors are red, orange, yellow, green, blue, and violet.

• These colors make up the visible light spectrum.

• These colors appear in the same order that they appear in a rainbow.

• They are arranged by wavelengths and frequencies.

Prisms

• A piece of glass called a prism separates white light into its different wavelengths.

• A prism lets you see the colors.

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Light and Matter

• Light rays travel in straight lines as long as nothing is in their way.

• When light rays strike an object they may pass through it, reflect off it or be absorbed by it.

Refraction

• Light changes speed when it passes into a new medium.

• When this happens the light bends.

• This bending is called refraction.

Reflection

• Light waves reflect at least a little off most objects.

• Reflection occurs when light rays bounce off, or reflect from a surface.

• Objects with smooth, shiny surfaces reflect more light rays than other surfaces.

Absorption

• Objects may absorb some light rays.

• Absorption occurs when an object takes in a light wave.

• After a light wave is absorbed it becomes a source of heat.

Multiple Choice

Which one of these objects would produce its own light?

• flowers

• chairs

• sun

• books

Multiple Choice

The discovery of what changed how people lived?

• flowers

• sunlight

• books

• fire

Multiple Choice

What happened in the 1900s?

• sun

• flowers

• inventions brought electrical energy into homes

Multiple Choice

The power plant might use?

• coal

• gas

• wind

• all of these answers

Multiple Choice

What is light energy that we can see?

• visible light

• moon

• invisible light

Multiple Choice

Which color is NOT in white light?

• black

• red

• orange

• green

Multiple Choice

What separates light into different wavelengths?

• rainbows

• sunlight

• prism

Multiple Choice

Bending of light is called what?

• reflection

• refraction

• absorption

Multiple Choice

What is called when light waves bounce off of a surface?

• reflection

• refraction

• absorption

Multiple Choice

This occurs when an object takes in a light wave.

• refraction

• reflection

• absorption