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Lesson · Grade 8 · Science

Transparent, translucent or opaque: what materials do to light

  • Grade 8
  • Science
  • 1 min 43 s
  • British Columbia
  • BC8-SC-36

The same light shines at clear glass, frosted glass and wood, and one labelled diagram builds up to show the light transmitted, scattered, or reflected and absorbed, so each material is named transparent, translucent or opaque. A side card then uses the same ideas to explain why a red shirt looks red and why the sky is blue (air scatters blue light much more than red, not a reflection of the ocean), and the video ends on a one-line recap of the three kinds of material.

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In one sentence

The question this lesson answers

What happens to light when it meets a material?

When light meets a material, it can be transmitted, absorbed, reflected or scattered.

Transcript

What the lesson says

What happens to light when it meets a material?

When light meets a material, it can be transmitted, absorbed, reflected or scattered.

We'll aim the same light at three materials: clear glass, frosted glass and wood.

Clear glass transmits almost all the light: it passes straight through.

So clear glass is transparent: you can see clearly through it.

Frosted glass transmits light too, but it scatters it, sending it off in many directions.

So frosted glass is translucent: light gets through, but shapes behind it look blurred.

Wood reflects some of the light, bouncing it back, and absorbs the rest, taking in its energy.

So wood is opaque: no light gets through, and there is a shadow behind it.

An opaque object's colour depends on which colours of light it reflects. White light is a mix of all colours.

A red shirt absorbs the other colours and reflects mostly red light, so it looks red.

Air is transparent, but it scatters a little of the sunlight, and it scatters blue light much more than red.

That scattered blue light reaches our eyes from all over the sky, so the sky looks blue.

The sky is not blue because it reflects the ocean. It is blue over deserts too.

Transparent materials let light straight through, translucent ones let it through but scatter it, and opaque ones let none through.

Curriculum

Where this fits

British Columbia, Grade 8

Science, Physics: light: behavioursBC8-SC-36

Previous: Lenses: How Convex and Concave Lenses Form ImagesNext: How the Eye Forms an Image

The outcomes and strands follow the British Columbia curriculum.

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