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1st Grade Science (Next Generation Science Standards) • Waves: Light and Sound

What Can Light Go Through?

Let's find out why you can see through a window but not through a book!

Explore the lesson 6 min read
A microscope with leaf and experiment flask for elementary science discovery
Inside this lesson 9 sections 4 questions 4 figures

SECTION 1

🔍 What's Happening?

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🔍 Anchoring Phenomenon

Now try holding up a book. Can you see through it? No! The light stops. What about a thin sheet of paper? You can see a little bit of light, but everything looks fuzzy.

Light ☀️GlassWindowLight goesALL through! ✅WaxPaperSOME lightgoes through 🔅Book📕✖NO lightgoes through! 🚫
A child holds three objects in front of a flashlight: clear glass, wax paper, and a book. Each one lets through a different amount of light.
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💭 Thinking Questions

SECTION 2

💡 What Scientists Know

Different things do different things to light. Some let all the light through. Some let a little light through. Some stop the light completely!

Scientists sort materials into three groups based on what they do to light.

1

Transparent

That means light goes all the way through. You can see clearly through it. A window is transparent!
2

Translucent

That means some light goes through, but it looks blurry. Wax paper is translucent!
3

Opaque

That means no light goes through. You cannot see through it at all. A book is opaque!

SECTION 3

🔬 Let's Try It!

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🔬 Let's Investigate!
  • Get a flashlight (or use a bright lamp).
  • Gather things from around your home: a clear cup, a piece of tissue paper, a piece of cardboard, a plastic bag, and anything else you want to test.
  • Hold each thing in front of the flashlight. Look at the other side. How much light do you see?
  • Sort each thing into a group: transparent, translucent, or opaque.

You are thinking like a scientist! Scientists test things and then sort them into groups. That is called classifying.

The Flashlight Test 🔦FlashlightCup👁️I can see!TRANSPARENT ✅Tissue😵‍💫Blurry!TRANSLUCENT 🔅Card-board✖🙈Nothing!OPAQUE 🚫Compare your results → Sort into groups!
The Flashlight Test: Shine a flashlight through a clear cup, tissue paper, and cardboard to see how much light passes through each.

SECTION 4

🧪 What We Found Out

When we test materials with light, we can compare what happens. Then we can sort them into groups!

Here is what we found when we tested different things:

MaterialWhat Happened to LightGroup
Clear glass cupAll the light went throughTransparent
Clear plastic bagAll the light went throughTransparent
Tissue paperSome light went through (blurry)Translucent
Wax paperSome light went through (blurry)Translucent
CardboardNo light went throughOpaque
BookNo light went throughOpaque

Look at the table. Materials that did the same thing to light go in the same group. That is how we classify them!

When something is transparent, light passes through and you can see clearly. When something is translucent, only some light passes through. Things look fuzzy. When something is opaque, no light passes through. You cannot see the other side at all.

SECTION 5

🔎 Do You See the Pattern?

Scientists love to find patterns. A pattern is when something happens the same way again and again.

Here is a pattern we found: Thick, heavy things usually block more light. Thin, see-through things usually let more light through.

This pattern works for many things in your life!

Where You AreWhat Lets Light Through?What Blocks Light?
At home 🏠Windows (transparent)Walls (opaque)
At school 🏫Glass door (transparent)Wooden door (opaque)
Outside 🌳Clear water (transparent)Rocks (opaque)
In the kitchen 🍳Plastic wrap (transparent)Aluminum foil (opaque)

SECTION 6

🌍 People Use This Science!

People use what they know about light and materials every day to solve problems!

1

🏠 Windows in Houses

Windows are made of transparent glass so sunshine can come in. That helps people see inside!
2

🕶️ Sunglasses

Sunglasses are translucent. They let some light through to help you see, but they block some light to keep your eyes safe.
3

🎪 Curtains

Curtains can be thick and opaque to block light when you want to sleep. Or thin and translucent to let soft light in.
4

☂️ Umbrellas

Umbrellas are opaque. They block sunlight to keep you cool on a hot day!
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🛠️ Design Challenge!

SECTION 7

📖 Words to Know

  • Transparent — Light goes ALL the way through. You can see clearly. (Example: a glass window)
  • Translucent — SOME light goes through, but things look blurry. (Example: wax paper)
  • Opaque — NO light goes through. You cannot see the other side. (Example: a book)
  • Classify — To sort things into groups based on what they are like.
  • Material — What something is made of. (Example: glass, paper, wood)

SECTION 8

✏️ Show What You Know!

Question 1: Warm-Up

Mia shines a flashlight at a piece of clear plastic wrap. She can see her toy dinosaur on the other side. What kind of material is the plastic wrap?
  • A. Transparent — light passes through and you can see clearly
  • B. Translucent — light passes through but things look blurry
  • C. Opaque — no light passes through
Show answer
The correct answer is A. Clear plastic wrap lets light pass straight through, so Mia can clearly see her toy dinosaur. That makes it transparent. Choice B is wrong because translucent materials make things look blurry or fuzzy — Mia could see the dinosaur clearly. Choice C is wrong because opaque materials block all light, and Mia would not be able to see through them at all.

Question 2: On Track

Leo holds a thick piece of cardboard in front of a lamp. No light comes through the cardboard. How should Leo classify the cardboard?
  • A. Transparent — because cardboard is flat
  • B. Translucent — because some light gets through
  • C. Opaque — because no light passes through
Show answer
The correct answer is C. Since no light passes through the thick cardboard, it is opaque. Choice A is wrong because being flat does not make something transparent — transparent means light passes through clearly. Choice B is wrong because translucent means some light gets through, but Leo observed that no light came through at all.

Question 3: On Track

Sara tests three materials by shining a flashlight behind each one. She writes down her results in a chart. A frosted shower curtain lets some light through, but Sara cannot clearly see objects behind it. How should she classify the shower curtain?
  • A. Opaque — it blocks all the light
  • B. Translucent — some light passes through but objects look blurry
  • C. Transparent — all light passes through clearly
Show answer
The correct answer is B. The frosted shower curtain lets some light through but objects behind it cannot be seen clearly. That is exactly what translucent means. Choice A is wrong because opaque materials block all light, and the shower curtain does let some light through. Choice C is wrong because transparent materials let you see things clearly on the other side, and Sara said she could not see objects clearly.

Question 4: Challenge

Jayden's class tested a window, wax paper, and a wooden block by shining light on each one. They found the window let all light through clearly, the wax paper let only some light through, and the wooden block let no light through. Which list correctly classifies all three materials?
  • A. Window = transparent, wax paper = translucent, wooden block = opaque
  • B. Window = translucent, wax paper = opaque, wooden block = transparent
  • C. Window = opaque, wax paper = transparent, wooden block = translucent
Show answer
The correct answer is A. The window lets all light through clearly, so it is transparent. The wax paper lets only some light through, making it translucent. The wooden block lets no light through, so it is opaque. Choice B is wrong because it mixes up all three categories — for example, it says the wooden block is transparent, but the class observed that no light went through it. Choice C is also wrong because it reverses the classifications — it calls the window opaque even though light passed through it clearly.

SECTION 9

🔮 What's Next?

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🔮 What's Next?

Varsity Tutors • 1st Grade Science (NGSS) • Waves: Light and Sound — Classifying Materials by How They Affect Light