Lesson C4: Reflection, Transmission, and Absorption

Key Ideas     Unit Checklist

  Video Lesson

Why does light pass through some objects but not through others? Watch this video to learn more about how objects reflect, transmit, and absorb light.

 
 

  Lesson C4: Reflection, Transmission, and Absorption


Figure C.2.4.1 – Reflective strips on a road reflect light at night.

Figure C.2.4.2– Reflective clothing makes people more visible.


Figure C.2.4.3– Traffic cones with reflective tape can be seen from a distance.
Reading and Materials for This Lesson

Science in Action 8
Reading: Pages 188–193

Materials:
Flashlight or other light source, block of wood, plastic grocery bag, plastic sandwich bag, clear glass of water, clear glass of milk, piece of tissue paper, sunglasses, piece of cardboard, aluminum foil, piece of glass, other materials you would like to test.

Reflective Safety Materials

Reflective materials help improve visibility and safety in dangerous situations. For example, traffic signs are covered in special reflective plastic films. If you look closely at a stop sign, you will notice it is covered with small shiny reflective cells. Reflective plastic markers are embedded into road marker lines. Special materials reflect light from car headlamps and streetlights, to improve the visibility of traffic markers from a distance.

Reflective materials are also used in safety clothing for people who work in dangerous situations such as construction and firefighting. People who ride bicycles or run at night often wear reflective clothing so that they are more visible to passing cars. Light reflecting off clothing makes a person more visible, which helps keep them safe.

 Watch More

It's Safe To Be Seen

Watch this video to see a demonstration of reflective safety material.

 
 

Figure C.2.4.4– Frosted glass is translucent.

Figure C.2.4.5– Transparent glass provides protection and visibility.



Figure C.2.4.6– Stained glass is found in many important buildings.
Light and Glass

Can you imagine living in a house with no glass windows? For much of human history, people did not have transparent windows in their homes. Although people have used glass to make containers for many years, glass windows have been common in homes for only about 400 years. 

Glass is a strong material that provides both protection and visibility. Today, glass is used in many structures. Transparent glass is useful in situations where a person needs to see clearly, but also needs a protective covering. For this reason, transparent glass is used for vehicle windshields and window panes in buildings. Translucent glass is useful in situations when light and protection is desired, but clear visibility is not necessary. Translucent frosted glass is often used in rooms such as bathrooms, to provide both light and privacy. 

 Watch More

The Magic of Glass

Why does light travel through glass? Watch this video to learn about how the particles in glass make it transparent.

 
 

  Try It! 


Transparent, Translucent, Opaque

Try this simple online simulation to view an object through different materials.

Instructions:

  1. Click here to open the online simulation.

  2. Click on material A. Drag it around the image. What do you observe?

  3. Click on material B. Drag it around the image. What do you observe?

  4. Click on material C. Drag it around the image. What do you observe?

Questions: 

Think about the following questions very carefully. Then, type or write your answers. After you have your answers, click the questions for feedback.


Material B is transparent because the material permitted light to completely pass through, forming a clear image.
Material A is opaque because the material did not permit any light to pass through, forming no image.
Material C is translucent because the material permitted light to pass through, but it also scattered light to create an out-of-focus image.

Lesson Activity

How Does Light Interact with Materials?

 Problem:

In this lesson activity, you will design and carry out an experiment to test if a material is transparent, translucent, or opaque.

Download:

DOWNLOAD this document. It provides a space for you to write your procedure. Also use the document to write answers to the analysis questions that come at the end of this activity.


Materials:

  • Flashlight, or other light source
  • Block of wood
  • Plastic grocery bag
  • Plastic sandwich bag
  • Clear glass of water
  • Clear glass of milk
  • Piece of tissue paper
  • Sunglasses
  • Piece of cardboard
  • Aluminum foil
  • Piece of glass
  • Other materials you would like to test

    Instructions:

    1. Write a numbered step-by-step procedure explaining how to test whether a material is transparent, translucent, or opaque. You need to consider how you will be able to tell the difference between the three types of materials.

    2. Carry out your procedure on the given materials, plus any other materials of your choice. Record your observations in a table like the one below; you will find one in the document you downloaded.


    Observations:

     

     


    Analysis Questions:

    Think about the following questions very carefully. Then, type or write your answers. When you have your answers, click the questions for feedback.

    Light passed completely through a transparent material. Light could be seen on the opposite side of a transparent material.
    Light passed through a translucent material and could be seen on the opposite side of the material. However, light passing through a translucent material was scattered and softer than light passing through a transparent material.
    Light did not pass through an opaque material. Light could not be seen on the opposite side of an opaque material.


    Figure C.2.4.7– Coloured glass bottles prevent light from disintegrating chemicals.

    Figure C.2.4.8– Stained glass windows are decorative and artistic.



    Figure C.2.4.9– Coloured camera filters block some colours of light from reaching a camera’s sensor.
    Coloured Glass

    Coloured glass is made by adding coloured mineral powders to melted glass. Coloured glass can be transparent or translucent. The colour of the glass is the same as the colour of light that can pass through the glass. For example, red glass allows red light to pass through.

    Coloured glass is used for different purposes. It is used for artistic decoration in stained glass windows. Some chemicals are stored in coloured bottles, such as brown bottles. This prevents light from entering the bottle and reacting with the chemicals. Coloured filters over photography lenses block some colours of light from reaching the camera sensor. This darkens and lightens parts of the image, especially in black-and-white photography. For example, a red filter lets red light pass through the camera to the sensor. This makes red objects in the picture appear lighter and other coloured objects in the picture look darker.

      Try It! 



    Coloured Filters and Light

    Try this simple online simulation, courtesy of PhET Interactive Simulations, to view how coloured glass filters affect light. 

    Instructions:

    1. Click here to open the online simulation.

    2. Highlight and click on the “Single Bulb” box, as shown below.

       

       

    3. Click the white light bulb and click on the red button to turn the flashlight on, as shown below.

       

       

    4. Click the black button over the grey line to put a coloured filter in front of the light beam, as shown below.

       

       

    5. Drag the slider on the colour spectrum to change the colour of the filter. What do you observe?

    6. Click on the particle flashlight beam, as shown below. What do you observe?

       

       


    Questions: 

    Think about the following question very carefully. Then, type or write your answer. When you have your answer, click the question for feedback.

    The colour of the filter is the same as the colour of light that passes through the filter. All other colours of light are absorbed by the filter.



      Make sure you have understood everything in this lesson. Use the Self-Check below, and the Self-Check & Lesson Review Tips to guide your learning.

    Unit C Lesson 4 Self-Check

    Instructions


    Complete the following 6 steps. Don't skip steps – if you do them in order, you will confirm your understanding of this lesson and create a study bank for the future.

    1. DOWNLOAD the self-check quiz by clicking here.

    2. ANSWER all the questions on the downloaded quiz in the spaces provided. Think carefully before typing your answers. Review this lesson if you need to. Save your quiz when you are done.

    3. COMPARE your answers with the suggested "Self-Check Quiz Answers" below. WAIT! You didn't skip step 2, did you? It's very important to carefully write out your own answers before checking the suggested answers.

    4. REVISE your quiz answers if you need to. If you answered all the questions correctly, you can skip this step. Revise means to change, fix, and add extra notes if you need to. This quiz is NOT FOR MARKS, so it is perfectly OK to correct any mistakes you made. This will make your self-check quiz an excellent study tool you can use later.

    5. SAVE your quiz to a folder on your computer, or to your Private Files. That way you will know where it is for later studying.

    6. CHECK with your teacher if you need to. If after completing all these steps you are still not sure about the questions or your answers, you should ask for more feedback from your teacher. To do this, post in the Course Questions Forum, or send your teacher an email. In either case, attach your completed quiz and ask; "Can you look at this quiz and give me some feedback please?" They will be happy to help you!

    Be a Self-Check

    Superhero!



    Self-Check Quiz Answers

    Click each of the suggested answers below, and carefully compare your answers to the suggested answers.

    If you have not done the quiz yet – STOP – and go back to step 1 above. Do not look at the answers without first trying the questions.


    The textured glass blocks are translucent. They allow light to enter the bathroom, but they scatter the light so that people cannot see clearly through the window, for privacy.
    The purpose of eyeglasses is to help people see objects more clearly. Eyeglasses are transparent so that light can pass through and form a clear image. If eyeglasses were translucent, light would scatter and form a blurry image.
    The light rays from spotlights high above the theatre stage spread out to cover a larger area on the stage. The performer is also lit with less intensity than if a light was placed directly beside the performer.
    Translucent lampshades scatter light and lower its intensity. This can create less harsh shadows in a room, changing the atmosphere.
    Windows have two sets of curtains to affect light in different situations. Sheer white curtains are translucent. These curtains scatter light and reduce its intensity on a sunny day, but they don’t completely block light. The second set of darker curtains are opaque. These curtains block light completely, which is useful in situations such as creating a dark bedroom for better sleep.