Light, Illumination, and Materials Grade 1

Content Topics Properties and actions of light Connection of light in air to light in space, versus light incident on a surface

Each color of light has its own energy. What is Light? Light is energy. Each color of light has its own energy. Openstax Image

All Types of Light (not included in standard) Openstax Image

Night Vision The primary source of infrared radiation is heat or thermal radiation. http://spaceplace.nasa.gov/ir-photo-album/en/

Constant Speed of Light (not included in standard) Light speed is constant in a vacuum (in space) 3 x 108 m/s 186,000 miles/sec 670 million mph It takes time for light to travel. New Horizons Fastest Spacecraft Launch 36,000 mph Image Credit: NASA

Some of Our Neighbors Sun 8 minutes Proxima Centauri 4.2 LY Sirius Andromeda Galaxy 2.5 x 106 LY

Practice If we look at Proxima Centauri in our night sky, which is 4.2 LY away, are we seeing it as it is now or as it was in the past? Explain.

How does “light” interact with matter? Light interacts differently with different types of matter.  Surface Material Angle Energy

Light energy gets absorbed Light bounces Light changes direction What does light do? Light travels Light energy gets absorbed Light bounces Light changes direction Light allows us to see objects

Examples of What Light Does Openstax Image

Practice What do opaque materials do? Block light, reflect light, and/or absorb light What are some examples of opaque materials? Wood Paper Bag Mirror

Transparent Materials Light travels through a material that is transparent. Light also travels through space. Air Air Glass Light Ray

Sunlight on Our Moon The Sun’s energy travels through space to the Moon. Light energy reflects from the Moon. Image Credit: NASA

We See Light Reflected from the Moon https://watchers.news/2011/09/21/how-can-we-see-the-sun-and-the-moon-at-the-same-time/ Simulation by watchersnews.com

Practice Do we see the light travel from a light to our desk? Do we see it move through the air? How do we know it is there? We cannot see the light traveling through a transparent material, like air. We know it is there because we see it reflected from objects that are at a distance from the light. We also know the light is in the air when we feel the sunlight. Do we see the light energy traveling through space from the Moon to us? How do we know that it does? We cannot see the light traveling through space. We know it is there because we see it reflected from the Moon.

Reflection Objects with very smooth surfaces bounce a lot of light from the surface. JWST Telescope Mirror Openstax Image

Smooth vs Rough Parallel Reflection Diffuse Reflection Light is bounced in a single direction Diffuse Reflection Light is bounced in various directions Openstax Images

Practice Parallel or Diffuse What type of reflection comes from your bathroom mirror? Parallel What type of reflection comes from wood kitchen cabinets? Diffuse

Our Atmosphere Sunlight passes through our atmosphere. Sunlight allows us to see objects.

Practice Can we see objects in the dark? When do we see objects? No, we cannot see objects if it is completely dark. When do we see objects? We see objects when there is light.

Atmosphere The atmosphere is a type of material. Light does different things depending on the material. Our atmosphere makes the light from stars look different. Fuzzy or Bleary Twinkling No stars

Twinkling Atmosphere Stars are like a light bulb. They shine bright and steady. The atmosphere causes starlight to change direction many times, so it looks like the stars are twinkling.

“Twinkle, twinkle, little atmosphere…” Video by pixabay.com