3.02 Light it Up! Part 1

3.02 Light it Up!

Did you ever wonder how we are able to see objects? The key ingredient is light. We can see sources of light, like the sun, fire, or a light bulb. To see other objects, a light source must be present. 

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Multiple Select

Select all the items that produce their own light which allows us to see them.

• Light bulbs

• Flowers

• Sun

• flashlights

• Apples

Light travels from a source and bounces off an object, then travels to our eyes.

• The sun is producing the light rays. The light travels through space in straight lines. She can see the object because the light rays reflect off the object and into her eyes.

Notes

• Light travels in straight lines.

• Some objects like light bulbs and the sun produce their own light.

• Other objects REFLECT light like apples and books.

Multiple Choice

What is producing the light rays?

• The sun

• Girl

• Statue

• Cloud

Multiple Choice

How are they traveling to Earth? Describe the path they take.

• The light travels in curvy lines to the girl.

• The light travels through space in straight lines.

• The light travels directly to the girl and she can see because she has eyes.

We can see objects because light reflects off of them and strikes our eyes. What happens if something stops light on its way to the object or our eyes? 

We can see this kitten's head poking out, but we cannot see its body behind the curtain. If there is a window back there, there should be enough light to reflect off its body, right? Why can we not see it?

• Well, the curtain is in the way, right? But what does that mean for the light?

• There is light reflecting off the cat, but that light is being absorbed by the curtain. The light does not reach our eyes, so we can't see it!

Notes

• refraction- when a wave bends as it moves from one medium to another

• reflection- when a wave strikes a surface and bounces off

  
  

• absorption- when a material captures the light energy of a wave

  
  

Light Reflected

• Light from the light source will reflect off objects and into our eyes. We can then see the objects.

• When the wall is removed, the observer can see the flower when the light reflects off of it and enters the observer's eyes.

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Light Blocked

• When the light from the source is blocked and does not reach our eyes, we cannot see objects.

• When there is a wall in front of the flower, the light cannot reflect off the flower and into the observer's eyes.

White Light, Many Colors

The light from most light sources is called white light, and it is made up of all the colors in the rainbow. 

If light has all of the colors, why are some things red and others green? How do we see colors? Light from a light source will travel outwards in a straight line until it hits an object. What happens, and what colors we see, depends on the object that the light strikes.

Black Objects

• When light strikes a black object, all of the light is absorbed. No light reflects to our eyes, and we do not see any color. .

• We see black. This also happens if the light is completely blocked from the object

White Objects

Light reflects off a white car, and all of it bounces off.

Green Objects

Red flower with green leaves. Sunlight is hitting the green leaf and reflecting green light into a girl's eyes.

Red Objects

Red flower with green leaves. Sunlight is hitting the flower and reflecting red light into a girl's eyes.

When white light shines through a prism it separates the light so you can see the different colors.

Raindrops act as tiny prisms to spread out the colors so you can see a rainbow!

• Blue Siding

  We see the blue siding on the house because the siding absorbs everything except blue. The blue color is reflected into our eyes.

• Green Leaves

  We see the green leaves on the trees because leaves reflect green light which enters our eyes.

• Red Monkey Bars

  We see the red monkey bars because the only light being reflected by them is the red light. Every other color is being absorbed.

• Purple Flowers

  These flowers look purple because they absorb every color of light except purple. The purple light is reflected into our eyes.

Multiple Select

What observations can you make about the light source in this image?

• The light is reflecting off of a book.

• The light is bending around the book.

• The light is entering the children's eyes.

• The flashlight is only shining red light.

• The light is traveling in a straight line.

Multiple Select

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What observation can you make from this image?

• Some light is being blocked by the lamp shade.

• Light from the lamp is traveling in one direction.

• The lamp is producing brown light.

• Light is coming from the lamp.

Straight Lines in All Directions

Light sources shine light in all directions. Depending on the source, some directions may be blocked. The headlights on the car are shining light on the path in front of the car, but not back onto the car itself, because the bulb is only directed forwards. If you look closely at the image of the streetlights, you can see rays of light pointing outwards in all directions. The sun shines in all directions, but is sometimes blocked by clouds. 

Notes

• Light travels in straight lines in ALL directions.

• Some directions can be blocked.

Open Ended

Think about a time when a light source was blocked and you couldn’t see the objects around you. Describe why you were unable to see those objects around you. Write your thoughts in your Science Notebook.

Reflections

• Light bulb

  The bulb is a light source. Even if nothing else was around, we would be able to see it because light can travel in a straight line directly into our eyes.

• Bicycle

  Some of the light that leaves the bulb is pointed at the bike. When it strikes the bike, it reflects, which means that it bounces off of the bike.

• Observer

  If the light bounces off of part of the bike and into the observer's eyes, he will be able to see it. Not all of the light that hits the bike will hit his eyes because it can bounce off in other directions.

Some objects reflect all of the light that shines on them and appear white. Other objects absorb all of the light that strikes them and appear black. Everything else will absorb some light and reflect some light, and the color that these objects appear depends on what gets reflected.

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