SME
Grade 6 Science · Physical Science
Light and matter: reflect, absorb, transmit
Use this for “Tinted glass reflects 30% of the light and absorbs 20%. What percent passes through?”
Diagram
30 + 20 + 50 = 100
This is an example. Type your own values to start a new problem.
r
%
+
a
%
+
t
%
=
100%
Formulas
30 + 20 + 50 = 100
Light reflected + light absorbed + light transmitted = all the light
Assumptions
•
When light hits a material, each bit of it is reflected (bounces off), absorbed (taken in) or transmitted (passes through).
•
The three parts add up to all the light that arrived: 100 percent.
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A mirror reflects most of it; black cloth absorbs most; clear glass transmits most; tinted glass does some of each.
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Absorbed light warms the material.
Step-by-step
WE KNOW
Light reflected: 30%
Light absorbed: 20%
FIND
light transmitted
Step 1 · Find light transmitted
30 + 20 + ? = 100
Light reflected + light absorbed + light transmitted = all the light
Whatever is not reflected or absorbed passed through.
Light transmitted = 100 − 30 − 20
Light transmitted = 70 − 20
Light transmitted = 50%
Check
Put the numbers back in. Both sides should match.
30 + 20 + 50 = 100 ✓
Topic check
See what you know: 5 questions on this topic
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