Color of Light

Color of Light

Middle School

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Learning Objectives

• Explain that white light is a mixture of colors; relate color to frequency.

• Describe how light travels straight and interacts with materials by different processes.

• Explain how refraction separates light and determines an object’s reflected color.

• Compare the mixing of colored light with the mixing of colored pigments.

Key Vocabulary

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Refraction

The bending of light as it passes between different media, such as from air to water.

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Wavelength

The distance between corresponding points of a wave, which is related to its perceived color.

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Frequency

The number of waves that pass a fixed point per second, which also determines color.

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Amplitude

The maximum height of a wave from its resting position, which determines the light's brightness.

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Transmission

The process where light successfully passes through a material instead of being absorbed or reflected.

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Absorption

The process by which an object takes in light energy, often converting it into heat.

Key Vocabulary

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Prism

A prism is an optical tool that refracts or bends light, separating it into its colors.

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Pigment

This is a type of chemical that appears colored because it absorbs certain wavelengths of light.

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Rod Cells

These are cells in the retina of your eye that are able to detect low light.

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Cone Cells

These are special cells in the retina of your eye that allow for color vision.

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The Spectrum of Light

• White light is a mixture of all colors, traveling in straight lines.

• When light enters a prism, it slows down and refracts, or bends.

• Each color's frequency causes it to bend at a slightly different angle.

• This separation creates the visible spectrum of colors, known as ROYGBIV.

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Multiple Choice

What is white light?

• A mixture of all colors of light

• The complete absence of light

• A single, pure color of light

• Light that has been filtered by a prism

Multiple Choice

What is the relationship between a color's frequency and the way it passes through a prism?

• The prism adds new colors to the white light.

• Each color has a different frequency that bends at a unique angle.

• The prism makes all the colors travel at the same speed.

• White light is made of only one color that the prism multiplies.

Multiple Choice

If a new type of glass was invented that caused all frequencies of light to bend at the exact same angle, what would happen if white light passed through a prism made of it?

• The light would bend but would remain white.

• The colors of the spectrum would appear in a reversed order.

• The light would pass straight through without bending.

• Only the color red would be visible after the prism.

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Wave Properties of Light

• A wave model is used to explain many of light's behaviors.

• The frequency of a light wave determines its color.

• The amplitude of a wave determines the light's brightness or intensity.

• Light waves can travel through the vacuum of space without a medium.

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Multiple Choice

What is used as a model to explain many of the behaviors and properties of light?

• A wave model

• A particle model

• A magnetic model

• An electrical model

Multiple Choice

What is the relationship between a light wave's properties and its appearance?

• Frequency determines its color, and amplitude determines its brightness.

• Frequency determines its brightness, and amplitude determines its color.

• Frequency determines its speed, and amplitude determines its path.

• Frequency determines its path, and amplitude determines its speed.

Multiple Choice

Why can sunlight reach Earth even though space is mostly empty?

• Sunlight uses air in space to travel.

• Sunlight cannot travel through empty space.

• Sunlight can travel through the vacuum of space without a medium.

• Sunlight travels slower in space than in the atmosphere.

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Frequency and Refraction

High-Frequency Light

• Light with a higher frequency, like violet light, has a much shorter wavelength.

• Because of its higher frequency, it bends more when it enters a new medium.

• This significant bending causes colors like violet to separate out distinctly in a spectrum.

Low-Frequency Light

• Light with a lower frequency, such as red light, has a longer wavelength.

• Due to its lower frequency, this light bends the least when passing through a medium.

• This minimal bending places red light at the opposite end of the visible color spectrum.

Multiple Choice

How does the frequency of light relate to the amount it bends when passing into a new medium?

• Higher frequency light bends more, while lower frequency light bends less.

• Higher frequency light bends less, while lower frequency light bends more.

• Frequency does not affect how much light bends.

• All frequencies of light bend by the same amount.

Multiple Choice

What are the key differences in the properties of high-frequency violet light and low-frequency red light?

• Violet light has a shorter wavelength and bends more, while red light has a longer wavelength and bends less.

• Violet light has a longer wavelength and bends less, while red light has a shorter wavelength and bends more.

• Both violet and red light have the same wavelength and bend by the same amount.

• Violet light is less dense than red light, which causes it to bend more.

Multiple Choice

What is the best explanation for why colors like red and violet appear at opposite ends of a spectrum?

• Light separates into a spectrum because higher-frequency colors bend more significantly than lower-frequency colors.

• Red light and violet light are naturally on opposite sides of any light beam.

• A medium filters out all colors except for red and violet, placing them at the ends.

• Lower-frequency light travels faster, causing it to separate from higher-frequency light.

How Objects Get Their Color

• An object's color depends on how it interacts with light.

• A red object reflects red light and absorbs other colors.

• White objects reflect all colors; black objects absorb all colors.

Multiple Choice

What is the primary factor that determines the color of an object?

• How it interacts with light

• The temperature of the object

• The size of the object

• The texture of the object

Multiple Choice

Which statement explains why a fire hydrant appears red?

• It absorbs red light and reflects other colors.

• It reflects red light and absorbs other colors.

• It reflects all colors of light equally.

• It absorbs all colors of light equally.

Multiple Choice

On a hot, sunny day, which surface would feel warmer to the touch: the black pavement of a road or the white painted line, and why?

• The white line, because it reflects all colors of light.

• The black pavement, because it absorbs all colors of light.

• The white line, because it absorbs most colors of light.

• The black pavement, because it reflects most colors of light.

Filters and Mixing Colors

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Color Filters

• ​A transparent colored object, like red glass, acts as a filter.

• ​​It transmits light frequencies corresponding to its own specific color.

• ​It absorbs most of the other frequencies of light passing through.

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Mixing Light (Additive)

• ​The primary colors of light are red, green, and also blue.

• ​​Combining these colors is an additive process to create new colors.

• ​Where all three light colors overlap, they will produce white light.

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Mixing Pigments

• ​Pigments create color by absorbing or subtracting certain light frequencies.

• ​​The primary pigment colors used are cyan, magenta, and yellow.

• ​Mixing these pigments absorbs more light, which in turn produces black.

Multiple Choice

How does a transparent colored object, such as red glass, function as a filter?

• It transmits its own color of light and absorbs other colors.

• It reflects all light, making it appear brighter.

• It absorbs all light, making everything appear black.

• It changes the color of light into a new primary color.

Multiple Choice

What is the primary difference in the outcome when mixing primary colored lights versus mixing primary colored pigments?

• Mixing lights is an additive process that creates white, while mixing pigments is a subtractive process that creates black.

• Mixing lights produces secondary colors, while mixing pigments produces primary colors.

• Mixing lights results in black, while mixing pigments results in white.

• Both processes are additive, but they use different primary colors to achieve their results.

Multiple Choice

A shirt is colored with a yellow pigment, which works by absorbing blue light. If you shine only pure blue light on the shirt, what color will it appear to be?

• Black, because the yellow pigment absorbs blue light.

• Green, because yellow and blue light mix to make green.

• Yellow, because the pigment's color does not change.

• Blue, because that is the only color of light available.

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Common Misconceptions

Misconception	Correction
An object has its own color.	An object's color depends on the light it reflects.
Light needs a medium like air to travel.	Light can travel through the vacuum of space.
Mixing colored paints and lights is the same process.	Mixing paint is a subtractive process; mixing light is additive.
Light waves themselves are colored.	Color is the perception of different light frequencies by our brain.

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Summary

• Light travels in a straight line and its color depends on its frequency.

• White light is a mixture of all colors and can be separated by a prism.

• An object's color depends on the light it reflects, absorbs, or transmits.

• Mixing colored light is an additive process, while mixing pigments is subtractive.

Poll

On a scale of 1-4, how confident are you about the concepts covered in today's review?

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