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Makerspace Light Link: Brightness or Pulses?

Grade 8 practice: a makerspace's fiber-optic thermometer tests show how lost light and stray sunlight change an analog signal but not a digital one.

Grade 8ScienceInteractive · Printable

Aligned toMS-PS4-3

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What’s included

Single worksheet
Auto-graded online
1 NGSS standard
Printable answer key
10 questions
Classroom-ready

Details

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

About this worksheet

What students practice

Students use test data to compare how lost light and extra light change analog and digital signals.
Students explain why on-off light pulses carry a reading more reliably than brightness does.
Students identify limits where a digital signal can also fail.

How to use

Use after introducing analog and digital signals. Have students trace one 25 °C reading through both versions before they start the questions.

Curriculum

NGSS standard covered

MS-PS4-3

Explain why digital signals carry information more reliably than analog signals.

Preview

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Name Date

Makerspace Light Link: Brightness or Pulses?

Test an analog and a digital way to send a temperature along an optical fiber.

Part 1: Light lost along the fiber

Read the build notes and study Table 1. Then answer the questions.

The Seed Shelf Thermometer

1The Eastgate Community Makerspace is a shared workshop where neighbors build and repair things. Its back room has a warm shelf for starting vegetable seedlings, and volunteers wanted to check the shelf's temperature from the front desk, 6 m away. Eighth grader Mina Szabo and volunteer Mr. Florian Abara built a thermometer that sends its reading to a display at the desk through a plastic optical fiber, a thin, bendable strand that guides light from one end to the other. The reading has to be trustworthy: many seeds sprout slowly when the soil is much colder than about 20 °C, and young seedlings can dry out and wilt when it gets much hotter than about 30 °C.

2They built two versions. In the analog version, the brightness of a small light at the shelf end follows the temperature: the light sends 4 light units for every degree Celsius, so 25 °C is sent as 100 units. The display divides the light it receives by 4 and shows the result as the temperature.

3In the digital version, the sensor turns the temperature into a pattern of short pulses. Each pulse is either fully on (100 units sent) or off (0 units sent). The display reads any pulse that arrives with 30 units or more as on and any pulse with less than 30 units as off. The pattern of on and off pulses stands for the temperature, and the display shows that number.

4To test the link, Mina held the shelf at 25 °C, checked with a lab thermometer, and routed the fiber in four ways. Each tight loop in the fiber lets a little light leak out, and dust on a connector blocks some light. For each route she measured how much of a 100-unit flash arrived at the desk, then read both displays.

5Next, Mr. Abara wondered about skipping the fiber and simply aiming the light across the room at the desk. Light from a window would then reach the display's detector along with the signal. Mina tested the reading at three times of day and recorded how much extra light from the window reached the detector. Table 2 shows the results.