Worksheet

Colored Lights and a Noisy Mixer

Grade 8 waves practice: use colored-light and mixer-noise tests in a home kitchen to model reflection, absorption, transmission and bending.

Grade 8ScienceInteractive · Printable

Aligned toMS-PS4-2

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Single worksheet
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1 NGSS standard
Printable answer key
10 questions
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Details

Format: Interactive · Printable
Grade: Grade 8
Subject: Science
Question types: Fill in the blank, Multiple choice, Sorting, Short answer

About this worksheet

What students practice

Students use colored-light observations to explain an object's color as the light it reflects.
Students use sound-level data to model how a door and a blanket reflect, absorb and transmit sound.

How to use

Read the passage together and, if you can, repeat the colored-light test with a phone flashlight and colored film. Ask students to name the wave behavior before they choose an answer.

Curriculum

NGSS standard covered

MS-PS4-2

Model how light and sound waves are reflected, absorbed or transmitted through different materials.

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Colored Lights and a Noisy Mixer

Model how kitchen light and sound are reflected, absorbed or transmitted.

Part 1: Food under colored lights

Read the passage and Leilani's light table, then answer the questions.

Night Baking in the Marchetti Kitchen

1Leilani Marchetti bakes for her school's fall bake sale every year. This year her family put color-changing LED strips under the kitchen cabinets. One night, with the strips set to blue, she noticed that the strawberries on her cutting board looked almost black. A wooden spoon standing in a glass measuring cup of water also looked odd: it seemed broken at the water's surface, even though it was straight when she pulled it out.

2Her science teacher had explained that white light is a mix of many colors, and each color is light with a different wavelength. When light reaches an object, the object can reflect it, absorb it or transmit it, which means letting it pass through. What we see is the light that reaches our eyes. Light travels in straight lines, but its path bends where it passes from one clear material into another, such as from water into air.

3Leilani planned a test. She turned off every other light in the kitchen and set the LED strips to white, then red, then green, then blue, keeping the brightness the same. She placed each object on the same spot on the counter, 30 cm below the strips, and wrote down how it looked in each color. Her dad checked her notes by looking at the objects with her.

4Next she tested sound. While her mom whipped cream with the stand mixer on its highest speed, Leilani stood in the hallway 3 m from the mixer and measured the sound level with a sound-meter app. She measured with the kitchen door open, with the wooden door closed, and with a heavy blanket hung over the closed door. She also measured the hallway with the mixer turned off. A higher decibel (dB) number means a louder sound, and a drop of about 10 dB makes a sound seem about half as loud.

5Last, her brother Mateus tapped the far end of the stone countertop lightly with a spoon. Leilani listened from 2 m away, first with her ear pressed against the countertop and then with her head lifted into the air. The taps sounded much louder with her ear on the stone.

How each object looked (Leilani's notes)
Object	White light	Red light	Green light	Blue light
Ripe strawberry	Red	Red	Very dark	Very dark
Lime	Green	Very dark	Green	Very dark
White plate	White	Red	Green	Blue
Blue mixing bowl	Blue	Very dark	Very dark	Blue

Under blue light, the strawberry looked very dark, but the white plate looked bright blue. What explains the dark strawberry?

A. The blue light was too dim to reach the counter where the strawberry sat.
B. The strawberry absorbed most of the blue light, so little light reached her eyes.
C. The blue light changed the red color inside the strawberry into black.
D. The strawberry transmitted the blue light through to the counter below it.

Which model best describes what happens when red light from the LED strip hits the lime?

A. Most of the red light is absorbed, and very little is reflected.
B. Most of the red light is reflected, so the lime looks red.
C. Most of the red light passes through the lime and lights the counter.
D. The lime turns the red light into green light and reflects it.

Use the table. Sort each object and light color by what the object does with most of that light.

Strawberry in red lightLime in blue lightWhite plate in green lightBlue bowl in red lightBlue bowl in blue lightStrawberry in green light

Mostly reflected	Mostly absorbed

Use paragraphs 1 and 2. Why did the straight wooden spoon look broken at the water's surface?

A. The water pushed the lower part of the soft spoon to one side.
B. Light from the lower part bent as it passed from water into air.
C. The glass reflected a second picture of the spoon onto the water.
D. The water absorbed the light from the lower part of the spoon.

Part 2: The mixer and the countertop

Use paragraphs 4 and 5 and the sound table to answer the questions.

Sound level in the hallway, 3 m from the mixer
Setup	Sound level (dB)
Kitchen door open	74
Wooden door closed	60
Closed door with blanket	54
Mixer off	35

Closing the wooden door lowered the sound level in the hallway by dB.

Compare "Kitchen door open" with "Closed door with blanket." Use the rule in paragraph 4: each 10 dB drop makes a sound seem about half as loud.

With the door closed and the blanket in place, the mixer seems about as loud as with the door open. (Write a fraction.)

Which model best explains why the hallway was quieter with the wooden door closed?

A. The door reflected and absorbed part of the sound, so less was transmitted.
B. Sound waves travel through air but stop when they reach a solid door.
C. The closed door made the mixer's motor spin more slowly and quietly.
D. The door blocked the mixer, and the 60 dB came from other hallway noise.

Hanging the blanket over the closed door lowered the level by another 6 dB. What is the best explanation?

A. The blanket reflected the sound toward the hallway, away from the kitchen.
B. The blanket kept the kitchen warm, and warm air carries less sound.
C. The blanket added new sound waves that canceled the mixer's sound.
D. The thick blanket absorbed some sound the bare door would have let through.

The spoon taps sounded much louder with Leilani's ear pressed on the stone countertop than through the air at the same distance. Which conclusion does this support?

A. Sound travels through solids, but it does not travel through air.
B. The stone made extra sound energy as the taps moved through it.
C. The stone transmitted the taps' vibrations to her ear better than air did.
D. Her ear on the stone blocked the sound of the mixer in the room.

10.

Mateus says, "A strawberry is red, so it should look red under any color of light." Do you agree? Write a claim, give evidence from Leilani's light table and explain your reasoning using the words reflect and absorb.