Physics C17N

Chapter 17: Optics and Light Interactions

Light Bounces off of a surface

​​Reflection

​​Refraction

​​Dispersion

Interference

Light Bends as it changes media

Light Waves Add Together and Cancel Out when they interact with each other

Different Frequencies of Light Spread Out in different ways as they pass through a medium

Diffraction

Light Waves Spread Out as they pass through an opening

Internal Reflection occurs when a light ray's refraction causes it to become "trapped" in a medium.

​Refraction

Specular reflections produce clear, crisp images because they reflect all wavelengths equally.

Diffuse reflections scatter light, causing some wavelengths to reflect more prominently.

​Reflection

​Key Vocabulary Review

The Index of Refraction varies for different wavelengths of light. As light refracts, it can be split into its component wavelengths.

Dispersion is caused by a combination of Refraction and Internal Reflection.

​Dispersion

As White Light enters a raindrop, it refracts. Each wavelength of the light refracts slightly differently, so the colors split.

Step 1: Refraction

The colored light bounces off of the inside of the raindrop. The curve of the drop causes the colored light to spread apart even more.

Step 2: Reflection

​As the light exits the raindrop, it refracts again, further splitting the colors of light and creating the rainbow that we see.

Step 3: Refraction

​How to Build a Rainbow: Step-by-Step

Multiple Choice

Which property of light causes dispersion?

• Different wavelengths have different indices of refraction

• Different wavelengths have different angles of internal reflection

• Internal Reflection produces more specular reflections than diffuse reflections

• Different indices of refraction cause different angles of internal reflection.

Polarized light is light that all oscillates in the same direction. Polarization does not affect interference in most applications.

Polarization

Constructive interference occurs when two waves overlap and build upon each other.

Destructive interference occurs when the two waves cancel each other out.

Interference

​Key Vocabulary Review

Incoherent Light is light in which the waves do not have the same wavelength.

Monochromatic Light is light where all of the wavelengths are the same.

Coherent Light is light that has the same wavelength and all of the crests aligned with each other.

Interference Vocabulary

Multiple Choice

Select which of the following is true about this light sample:

• It is coherent, but not monochromatic

• It is monochromatic, but not coherent

• It both coherent and monochromatic

• It neither coherent nor monochromatic

Multiple Choice

Select which of the following is true about this light sample:

• It is coherent, but not monochromatic

• It is monochromatic, but not coherent

• It both coherent and monochromatic

• It neither coherent nor monochromatic

Multiple Choice

Select which of the following is true about this light sample:

• It is coherent, but not monochromatic

• It is monochromatic, but not coherent

• It both coherent and monochromatic

• It neither coherent nor monochromatic

Multiple Choice

Can light be coherent without being monochromatic? Why?

• Yes, because the light could be polarized.

• No, because coherent light has to all have the same wavelength

• Yes, because multiple colors of light have the same wavelength

• No, because monochromatic light is not polarized.

Multiple Select

Can light be coherent without being polarized? Why?

• Yes, because coherence requires the waves have the same wavelength, not the same direction

• No, because polarizing light makes its wavelength change.

• Yes, because polarizing light just changes its direction, not its wavelength.

• No, because monochromatic light is not polarized.

​Light that is both coherent and monochromatic will interfere the most noticeably, producing regions of light and darkness.

When light passes through an opening or around a barrier, it will Diffract, or bend. All waves share this property.

The smaller the gap, the more the waves will bend.

​Diffraction

When a surface is covered in tiny ridges or bumps, each ridge causes light to be reflected, dispersed, and diffracted differently. As these different waves interfere with one another, certain wavelengths will become more or less powerful. This causes the shifting rainbow patterns of Iridescence: a phenomena when the observer sees different colors depending on which angle they observe the object from.

Interference and Diffraction Work Together

​Multi-Slit Diffraction

Dropdown

Choose the word that completes the sentence:

1. Soap bubbles are a great example of optics. First, as light passes through the soap layer and enters the bubble, it

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and changes direction.

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2. As the light changes direction in the soapy layer, it

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,splitting into multiple different wavelengths.

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3. Next, all of the wavelengths of light travel through the middle and then will

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off of the sides of the bubble multiple times

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As the light passes itself over and over, all of the wavelengths of light

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with each other, both constructively and destructively.

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Tiny bumps and imperfections in the soap layer of the bubble cause the light to

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as it finally exits.

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