Book cover for Living by Chemistry

Living by Chemistry

Angelica M. Stacy

ISBN #9781464142314

2nd Edition

943 Questions

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44,864 Students Helped

Homework Questions

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Summary
Learning Objectives
Key Concepts
Example Problems
Explanations
Common Mistakes

Summary

This section explains how light, as a form of energy, is emitted from sources like the Sun and light bulbs, travels through space as rays, and interacts with matter through reflection, transmission, and absorption. It covers the concept that white light is a combination of multiple colors, which can be separated by a prism and recombined, and introduces the wave model of light to explain properties such as wavelength and frequency. Understanding these processes is vital for grasping how we perceive colors and the nature of light energy.

Learning Objectives

1

Explain how light is emitted from various sources and travels as rays through space.

2

Describe the interaction of light with matter through reflection, transmission, and absorption.

3

Understand how white light contains a mixture of colors and how prisms can separate and recombine these colors.

4

Analyze the wave model of light, including concepts of wavelength, frequency, and speed.

Key Concepts

CONCEPT

DEFINITION

Emission

The process by which a light source produces and releases light energy, often through thermal energy or other forms of energy conversion.

Radiation

The transfer of energy through space or a medium in the form of waves or particles; light is one form of electromagnetic radiation.

Light Ray

A simplified model that represents the straight-line path that light travels, used to trace how light interacts with objects.

White Light

A mixture of all the colors of the visible spectrum; it can be separated into its component colors using a prism.

Reflection

The bouncing of light off a surface. Smooth surfaces reflect light in a uniform direction, while rough surfaces scatter light in multiple directions.

Transmission

The passage of light through a medium or a transparent material with little to no absorption.

Absorption

The process by which an object takes in light energy, often converting it into other forms of energy, causing the object to appear colored based on the light it reflects.

Wavelength

The distance between consecutive peaks (or troughs) in a wave, which determines the color of light in the visible spectrum.

Frequency

The number of complete wave cycles that pass a given point per unit of time, related to the energy of the light wave.

Wave Model of Light

A representation of light that describes it as a wave, useful for explaining phenomena such as interference, diffraction, and the propagation of light through space.

Example Problems

Example 1

How could you provide evidence that light is a form of energy?

Example 2

Provide an explanation as to why we see colors.

Example 3

What color will you see if you shine white light through a piece of thin blue plastic?

Example 4

What color will you see if you shine blue light through a piece of thin blue plastic?

Example 5

What color will you see if you shine white light from a l ashlight onto a green car at night?
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Step-by-Step Explanations

QUESTION

How does a green leaf appear green when illuminated with white light?

STEP-BY-STEP ANSWER:

Step 1: Recognize that white light is composed of a mixture of various colors.
Step 2: Understand that when white light hits a green leaf, the leaf absorbs most of the colors except green.
Step 3: Realize that the green light, which is not absorbed, is reflected from the leaf.
Step 4: Conclude that the reflected green light enters your eyes, making the leaf appear green.
Final Answer: A green leaf appears green because it absorbs other colors in white light and reflects the green wavelengths.

Colored Objects and Light Absorption

QUESTION

Why does a blue car appear black under a yellow streetlamp?

STEP-BY-STEP ANSWER:

Step 1: Understand that a yellow streetlamp emits predominantly yellow light.
Step 2: Recall that a blue car’s surface is designed to reflect blue light and absorb other colors.
Step 3: Note that since yellow light does not contain the blue wavelength, the blue car absorbs most of the yellow light.
Step 4: Recognize that very little light is reflected back to your eyes.
Final Answer: Under yellow light, a blue car appears black because it cannot reflect the yellow wavelengths it absorbs, leaving it with little visible light.

Streetlamp and Car Colors Example

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Common Mistakes

  • Confusing the ray model with the wave model of light; while the ray model shows the path of light, it does not explain its wave properties.
  • Assuming that objects produce their own light rather than reflecting or transmitting light from external sources.
  • Misunderstanding color perception by not recognizing that the color seen is due to selective absorption and reflection of light wavelengths.
  • Overlooking the fact that even though light travels in straight lines, its path can only be visualized when it interacts with particles like dust or water droplets.