Light

Kristin Adams

Light Energy

The form of light energy that we see is called visible light. Light energy travels from its source as waves. Like all waves, light waves have wave lengths and frequencies. White light, from such sources as a lamp or sun, are actually a blend of colors. The human eye actually sees red, blue and green, the rest of the colors we see are a blend of the three. These colors make up the visible light spectrum. The colors in the visible light spectrum always appear in the same order in which they appear in a rainbow, red, orange, yellow, green, blue, indigo and violet, and are arranged by wavelengths and frequencies.

The Spectrum Song by Ludwig von Drake

The Spectrum Song

Prisms

A piece of glass called a prism separates light into its different wavelengths. The prism will let you see the colors. As you move from red to violet on the visible light spectrum the wavelength decreases and the frequencies increase. Refraction causes the white light to bend when it hits the prism. The white light separates into individual colors you can see because each color bends differently.
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Wavelengths of Color

As the full spectrum of visible light travels through a prism, the wavelengths separate into the colors of the rainbow because each color is a different wavelength. Violet has the shortest wavelength, at around 380 nanometers, and red has the longest wavelength, at around 700 nanometers.

Rainbow Formation by www.makemegenius.com

Rainbow Formation - How & Why -Education video for kids from www.makemegenius.com

Raindrops can cause light waves to bend, what other things can cause a rainbow to form?

Light and Matter

Light travels in straight lines - as long as nothing gets in their way. But when light hits an object it they may pass through it, bounce off it or be absorbed by it.

Refraction

Refraction of light is when light bends when passing through one substance to another. The light bends because the speed of a wave changes when a wave moves from one medium to another. This change in wave speed is accompanied by a change in wavelength and change in direction.

What type of objects refract light?

  • Prisms
  • Cut Diamonds
  • Water
  • Soap Bubbles
  • Microscope Lenses

Reflection

Reflection occurs when a wave traveling in one medium strikes the surface of a different medium and changes direction so that it returns back into the medium in which it was originally traveling in. Simply put the waves bounce back. How much reflection depends upon how even the surface is. If the surface is smooth and flat, the light will bounce off it at equal angles. That is why a flat mirror reflects a good likeness of the object being reflected.
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Look at the diagram above. Notice the angles at which the rays of light strike the surfaces.

What sort of objects reflect light?

  • Mirrors
  • Shiny Surfaces
  • Some Metal
  • Surface of Water

Refraction and Reflection Video

Reflection&Refraction Song

Absorbtion

Absorption occurs when an object takes in a light wave. After a light wave is absorbed, it becomes a form of heat.

Have you ever worn a black shirt on a sunny day? What happens?

What sort of objects absorb light?

Well, technically most items do absorb some light.

How does absorbtion help us to you see color?

When we see an object that is green, that is because the object is absorbing all of the colors EXCEPT for green. Green is bounced back to our eye and that is how we see them color.
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What about black and white?

When something appears black, it is absorbing all of the light. If an object appears white, none of the light is absorbed.
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The Wonderful World of Colour

The Wonderful World Of Colour

Light and Matter

When light travels through an object the way the light passes through the object can be described as transparent, translucent, or opaque.

Transparent

When light passes through objects, these objects can be easily seen through.

Traslucent

When light partially passes through objects, these objects cannot be easily seen through.

Opaque

When light cannot pass through objects, these objects cannot be seen through.
ADLC - Elementary Science: Translucent, Transparent, Opaque

Answer the following questions with your partner in your Science Journal

  1. Explain why the visible light spectrum has different colors.
  2. What happens to an object that absorbs a lot of light?
  3. Describe how light bends, or refracts, when traveling through different objects.
  4. How will a flat surface reflect light?
  5. What ways can an object be described when light travels through it?

Create a foldable with the following vocabulary for this lesson

  • Translucent
  • Transparent
  • Opaque
  • Reflection
  • Refraction
  • Absorption
  • Visible Light
  • Visible Light Spectrum
  • Prism