How do optical devices help scientists learn more about the world? Watch this video to learn more about optical devices like telescopes and microscopes.
Lesson C3: Optical Devices
Figure C.1.3.1 – Telescopes help people see distant objects in space.
Figure C.1.3.2 – The Hubble Space Telescope orbits the Earth.
Figure C.1.3.3 – The Hubble Space Telescope captures amazing images of space.
Reading and Materials for This Lesson
Science in Action 8
Reading: Pages 182–186
Materials:
2 paper cups (same size), black acrylic craft paint, paintbrush, thumbtack, pencil, waxed paper, rubber band,
black electrical tape, scissors.
Figure C.1.3.4 – Liquid mirror telescopes are larger than glass refracting telescopes.
Telescopes
Telescopes enable humans to study space in more detail. Galileo was the first scientist to use a telescope to study space. During the 1600’s in Italy, Galileo discovered distant parts of the solar system that had not yet been observed. Galileo’s telescope
observations helped him to confirm the scientist Copernicus’ theory that the Earth and other planets rotated around the Sun.
We still use telescopes today to study distant space beyond the solar system. Most large modern telescopes use mirrors, because large glass lenses are difficult to make and move around. The Hubble Space Telescope is a satellite that orbits the Earth,
so the telescope can collect light from distant stars without interference from Earth’s atmosphere.
Some telescopes use liquid metal to collect light, instead of a solid metal mirror. Liquid mirror telescopes contain shiny liquid mercury metal in a circular rotating pan. Liquid mirror telescopes are less expensive to produce than similar solid mirror
telescopes. However, liquid telescopes can only collect light from straight above them, to keep the liquid metal in the pan. Canada has the largest liquid mirror telescope in the world, at the University of British Columbia.
Watch More
Using Light to See Very Far Away
This video shows how large telescope mirrors are made inside a factory.
This video briefly covers the history of telescopes, up to the James Webb IR telescope of 2018.
Connections
Figure C.1.3.5 – People use binoculars to view distant objects.
Figure C.1.3.6 – Stereoscopic reel toys combine two images to produce a 3-D image.
Figure C.1.3.7 – Slightly different images on a movie screen produce 3-D images when viewed through special glasses.
Connections – Literacy >> Binocular and Stereoscopic Vision
Human vision is described as both binocular and stereoscopic.
In the Latin language, the word “bini” means “two together”, and the word “oculus” means “eye”. Putting these two Latin words together gives us “binocular”, which means “two eyes together”. Binocular devices use both eyes. Binoculars for seeing distant
objects are made from two telescopes. Each eye looks through a telescope. Many scientists use binocular microscopes, which have two eyepieces.
When you view an object with both eyes, your brain produces a stereoscopic image. In the Greek language, the word “stereo” means “solid” or “three-dimensional”, and the word “skopein” means “to see”. Putting these two Greek words together gives us
“stereoscopic’, which means “to see in 3-D”.
Humans have natural stereoscopic vision. Because your eyes are slightly offset, each of your eyes collects slightly different light rays to produce two slightly different images. Your brain combines and interprets the two different images from your
eyes as a single 3-D image.
Binoculars, stereoscopic reel toys, virtual reality goggles, Google Cardboard, and 3-D movies make 2-D images appear to be 3-D. For example, 3-D movies are projected as two slightly different images on the screen. Special 3-D movie glasses filter light from the slightly different screen images, sending a slightly
different image to each eye. The brain combines and interprets the two different images as a 3-D image, which makes objects on the movie screen appear to pop out.
Figure C.1.3.8 – Scientists look through binocular microscopes with both eyes.
Figure C.1.3.9 – Virtual reality headsets make 2-D images appear to be in three dimensions.
Watch More
Stereoscopic Vision
Watch this video to see how binoculars are made.
This video explains how 3-D glasses and movies work.
Watch this video to learn more about 3-D vision and new 3-D technologies.
Connections
Figure C.1.3.10 – Early cameras were difficult to move and operate.
Figure C.1.3.11 – Modern cameras are digital and portable.
Connections – Technology >> History of Cameras
Cameras have changed a lot since their invention 200 years ago. The simplest type of camera is a camera obscura, or a pinhole camera. In the Latin language, “camera” means “chamber”, or “room”, and “obscura” means “dark”. Putting these two words together
gives us “camera obscura”, which is a “dark chamber”. A pinhole camera is simply a dark box with a tiny hole to let light rays enter. The light rays project an image inside the box.
Figure C.1.3.12 – A camera can capture many types of images depending on the lens used.
People used the camera obscura effect to project and trace images of objects. However, photography really took off when inventors created surfaces that were able to record light images. The first photographs were captured on glass plates coated with a
silver-based substance. The silver coating darkened when it was exposed to light, recording the opposite, or “negative” image. An image of the original object could be produced by covering a piece of light-sensitive photographic paper with the negative
and exposing it to light.
Eventually photographic film was developed to record images. Film is made of a roll of plastic covered with a light-sensitive substance. Early photographs were black and white because the film coatings only responded to white light. Scientists later
discovered chemicals that react to different colours of light, and used them to make colour film. Today, instead of film, cameras record images on a light sensor.
Cameras are useful tools for humans, far beyond taking selfies! Cameras have helped scientists record how things change over time. For example, photographs show evidence that the world’s glaciers are melting, because we can compare photographs of
glaciers from 100 years ago to today. Photographs help us share information with people around the world. Photographs record historical events and they are a popular art form.

Watch More
The History of Photography and Cameras
This video explains how early cameras were invented and how cameras have changed over time.
Watch this video to learn how pinhole cameras work.
Cameras help scientists make careful observations. Watch this video to learn more.
Try It!
Make a Pinhole Camera
Try making your own simple pinhole camera.
Materials:
2 paper cups (same size)
Black acrylic craft paint
Paintbrush
Thumbtack
Pencil
Waxed paper
Rubber band
Black electrical tape
Scissors
Safety Warning
Take care with scissors; don't cut yourself or anyone else!
Instructions:
Paint the inside of both paper cups completely black and let dry.
Turn both cups upside down. Use a pencil to mark the center on the bottom of each cup.
On one cup, push the thumbtack through the center marking to make a tiny hole. This is the pinhole.
On the other cup, push the pencil through the center marking to make a pencil-sized hole. This is the viewing hole.
On the pinhole cup, cut a square of waxed paper large enough to cover the open top of the cup, with about 3 cm extra on each side.
Use the rubber band to secure the waxed paper tightly to the top of the cup.
Place the open top of the viewing hole cup and the waxed paper end of the pinhole cup together, so that the pinhole and viewing holes are far apart. Tape both cups together with black electrical tape along their open edges, so that no light can
get into the cups.
Put your eye up to the viewing hole, and point the pinhole at different objects. 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.
You don’t see the world upside-down because your brain interprets the image in your eye as right-side-up.
Sharing:
Congratulations on completing this activity! Your teacher and other students would be interested in seeing the pinhole camera you built, so consider sharing your completed work (or any thoughts and experiences you might have regarding this activity)
in the course Sharing Forum. You can also email your completed work to your teacher and ask for feedback.
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 3 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.
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.
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.
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.
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.
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.
Most optical devices with lenses are small in size because their lenses are relatively small in size. Big pieces of glass are heavy and difficult to handle, which makes large glass lenses impractical for use in optical devices.
Microscopes allow humans to see tiny living organisms. Infectious diseases are caused by microorganisms like bacteria and viruses. Understanding the causes of diseases helps us find cures for diseases.
Without cameras to take photographs, communicating would become more difficult. It would also be more difficult to do scientific research, and more difficult to record and communicate historical events.
Looking through binoculars, each of your eyes receives a slightly different image. Your brain merges the two images to produce a 3-D image. You only use one eye to look through a telescope. Images viewed with just one eye look flat, or two-dimensional.
Reading and Materials for This Lesson
