Unit C Lesson C8 The Wave Model of Light
Completion requirements
Lesson C8: The Wave Model of Light
Video Lesson
Light is not the only type of energy that travels as a wave. Watch this video to learn more about some other types of energy that travels as waves.
Lesson C8: The Wave Model of Light
Figure C.2.8.1 – Different radio stations transmit radio waves with different frequencies.
Figure C.2.8.2– FM radio stations send radio signals with megahertz frequencies.
Figure C.2.8.3– Radio announcers provide news and entertainment to people over a large area using only radio waves.
Reading and Materials
for This Lesson
Science in Action 8
Reading: Pages 212–220
Materials:
No additional materials are required for this lesson.
Radio Stations
Radio waves are used to transmit radio signals. Radio waves can be characterized by their long wavelengths. However, radio waves are more often described by their frequency. The frequency of a wave describes how many wave cycles pass in one second. Frequency is measured in hertz, or Hz for short. One hertz is equal to one wave cycle per second.
The call numbers of radio stations describe the frequency of the radio waves used to transmit the station’s radio signal. FM radio stations have frequencies that are measured in megahertz, or MHz. A megahertz is one million hertz. For example, an FM radio station with a call number of 98.1 broadcasts radio waves with a frequency of 98.1 MHz, which is 98 100 000 wave cycles per second. AM radio stations broadcast radio waves in kilohertz, or kHz. One kilohertz is equal to 1000 hertz.
Radio waves are used to transmit radio signals. Radio waves can be characterized by their long wavelengths. However, radio waves are more often described by their frequency. The frequency of a wave describes how many wave cycles pass in one second. Frequency is measured in hertz, or Hz for short. One hertz is equal to one wave cycle per second.
The call numbers of radio stations describe the frequency of the radio waves used to transmit the station’s radio signal. FM radio stations have frequencies that are measured in megahertz, or MHz. A megahertz is one million hertz. For example, an FM radio station with a call number of 98.1 broadcasts radio waves with a frequency of 98.1 MHz, which is 98 100 000 wave cycles per second. AM radio stations broadcast radio waves in kilohertz, or kHz. One kilohertz is equal to 1000 hertz.
Watch More
I Can’t Live Without My Radio
Watch this video to learn more about AM and FM radio.
Watch this video to learn more about AM and FM radio.
Figure C.2.8.4– Digital devices like tablets connect to the internet with WiFi.
Figure C.2.8.5– A wireless router sends radio wave internet signals to digital devices.
What is WiFi?
Wireless internet, or WiFi, has only been in widespread use since the early 2000’s. Before WiFi, people had to plug an internet cable into computers and laptops.
WiFi uses low frequency radio waves to transmit internet signals to digital devices. Cable or phone lines carry internet signals into a building. A machine called a modem receives the internet signal from the cable or phone lines. The internet signal travels from the modem to the wireless router, which changes the digital signal into radio waves. The radio waves travel to digital devices connected to the WiFi network.
Wireless internet, or WiFi, has only been in widespread use since the early 2000’s. Before WiFi, people had to plug an internet cable into computers and laptops.
WiFi uses low frequency radio waves to transmit internet signals to digital devices. Cable or phone lines carry internet signals into a building. A machine called a modem receives the internet signal from the cable or phone lines. The internet signal travels from the modem to the wireless router, which changes the digital signal into radio waves. The radio waves travel to digital devices connected to the WiFi network.
Watch More
Wireless WiFi
Watch this video to learn more about how WiFi internet works.
Watch this video to learn more about how WiFi internet works.
Can you imagine not being able to use a cell phone or WiFi internet? Cell phones and WiFi are banned from a small town in the United States, because their radio waves would interfere with a nearby radio telescope. Watch this video to learn more.
Connections
Figure C.2.8.6– Police use radar to catch speeders.
Figure C.2.8.7– Airports use radar to determine the position of airplanes, especially on cloudy days.
Figure C.2.8.8– Radar allows air traffic controllers to see nearby planes and helicopters.
>> Radar
Radar is a technology that uses radio waves to determine the location of objects. A radar machine’s transmitter emits radio waves, which reflect off objects. The reflected radio waves return to the radar machine’s receiver. The time that it takes for the radio waves to return to the radar machine is used to calculate the location of the object. Radar can also determine how fast an object’s position changes, which is used to calculate the object’s speed.
Radar is used for several purposes. Police use radar to catch people who are driving faster than the speed limit. Weather forecasters use radar to determine the motion of clouds, as well as how much precipitation is contained in clouds. Airport traffic controllers and airplane pilots use radar to detect the position of airplanes in the sky.
Figure C.2.8.9– Weather stations use radar to track the movement of clouds.
Figure C.2.8.10– Weather forecasters create maps from weather radar information.
Watch More
Radar - Radio Detection And Ranging
Watch this video to learn more about how radar works.
Watch this video to learn more about how radar works.
Connections
Figure C.2.8.11– RFID microchips can be implanted under an animal’s skin.
Figure C.2.8.12– Tap-and-pay credit cards contain an RFID chip.
Figure C.2.8.13– Farmers and ranchers use RFID tags to track cattle.
>> Radio Frequency Identification
Radio frequency identification, or RFID, is a technology that uses radio waves to quickly identify and track objects.
Tap-and-pay credit cards and debit cards have a thin RFID computer chip. The RFID chip on the card reads a radio wave signal from the payment machine. The RFID chip sends a radio signal back to the machine to authorize the payment.
RFID chips are also used to track and identify animals on farms, such as cows and sheep. Livestock ear tags contain an RFID chip, to track and locate animals. Veterinarians are starting to implant RFID chips under the skin of pets, instead of using collar tags. This makes it easier for lost pets to be identified and returned to their owners.
Watch More
RFID Implants in Humans
Some humans are choosing to put RFID chip implants under their skin. RFID chips allow people to open doors or make purchases with just a swipe of their hand. Is this a useful technology or does it have some drawbacks? Watch this video to learn more about RFID implants.
Some humans are choosing to put RFID chip implants under their skin. RFID chips allow people to open doors or make purchases with just a swipe of their hand. Is this a useful technology or does it have some drawbacks? Watch this video to learn more about RFID implants.
Figure C.2.8.14– Doctors use X-ray images to diagnose broken bones.
Figure C.2.8.15– CT scanning machines take X-ray images from different angles of the body.
X-Rays
If a person breaks a bone, they usually get an X-ray image to confirm the location of the fracture. X-rays are high energy electromagnetic waves that are used to make an X-ray image. X-rays can pass through soft tissues. This is indicated by dark spots on an X-ray image. X-rays cannot pass through dense substances, like bones and metal. These solids show up as white shadows on X-ray images.
X-ray images can also be used to diagnose diseases. Abnormal spots on chest X-rays help diagnose diseases of the lungs, such pneumonia and lung cancer. A CT scanning machine takes X-ray images from different angles of the body. CT scans are used to diagnose abnormal tissues in the body, like cancerous tumours.
If a person breaks a bone, they usually get an X-ray image to confirm the location of the fracture. X-rays are high energy electromagnetic waves that are used to make an X-ray image. X-rays can pass through soft tissues. This is indicated by dark spots on an X-ray image. X-rays cannot pass through dense substances, like bones and metal. These solids show up as white shadows on X-ray images.
X-ray images can also be used to diagnose diseases. Abnormal spots on chest X-rays help diagnose diseases of the lungs, such pneumonia and lung cancer. A CT scanning machine takes X-ray images from different angles of the body. CT scans are used to diagnose abnormal tissues in the body, like cancerous tumours.
Figure C.2.8.16– X-ray images of teeth show dental problems hidden below the gums.
Figure C.2.8.17– Airport luggage scanners use X-rays to make sure baggage does not contain dangerous items.
Watch More
X-ray Vision
Why can X-rays see under your skin? Watch this video to learn more about X-rays.
Why can X-rays see under your skin? Watch this video to learn more about X-rays.
Connections
Figure C.2.8.18– It is a good idea to wear sunscreen outdoors.
Figure C.2.8.19– A sunscreen’s SPF number indicates how much UV radiation it blocks.
Figure C.2.8.20– Hats and swimsuit shirts help prevent sunburns.
>> Sun Smarts
The sun emits three types of ultraviolet radiation: UVA, UVB, and UVC. Most of the ultraviolet light that reaches Earth’s surface is lower energy UVA and UVB radiation. With exposure over time, UVA radiation causes skin wrinkling and aging. UVB radiation penetrates deeper into human skin, and causes sunburns. Most higher energy UVC radiation is blocked from Earth’s surface by ozone particles high in the atmosphere.
Too much exposure to ultraviolet radiation increases a person’s risk of getting skin cancer. Medical researchers have found that experiencing many sunburns as a child and teenager can greatly increase a person’s risk of getting skin cancer as a young adult. This increased risk also affects people with darker skin who don’t sunburn easily. Skin cancer is highly preventable. People can take many actions to avoid too much exposure to ultraviolet radiation. Staying out of the sun during the hottest part of the day stops exposure to UV radiation. Clothing that covers the skin, like hats and swimsuit shirts, also reduces UV radiation exposure.
Wearing sunscreen daily prevents skin damage from UV rays. Sunscreen blocks UV radiation from travelling deep into skin tissues. The SPF number on sunscreen describes the fraction of UV radiation that is able to penetrate the skin. Higher SPF sunscreens block more UV radiation. For example, a sunscreen with an SPF 60 only lets 1/60 of UV light rays through to the skin, which is a very small fraction.
Figure C.2.8.21– Skin cancer can spread to other parts of the body.
Figure C.2.8.22– Sun protection is most important when you are young.
Watch More
Sun Smarts
Watch this video to learn more about why wearing sunscreen is important to protect the body from UV radiation.
Watch this video to learn more about why wearing sunscreen is important to protect the body from UV radiation.
This video has some advice from adults who have experienced skin cancer.
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 8 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.
- DOWNLOAD the self-check quiz by clicking here.
- 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.
Radio waves have long wavelengths with lower energy. Radio waves do not pass through living tissue, unlike X-rays which can penetrate and damage living tissue.
A metal screen blocks X-ray waves. This reduces dental assistants’ exposure to X-ray radiation that can damage their body tissues.
Three types of electromagnetic radiation travel from the Sun to Earth’s surface.
- You detect visible light from the Sun with your eyes.
- You detect infrared radiation, or heat, from the Sun on your skin, with heat-sensing nerve cells.
- You detect the effects of ultraviolet radiation from the Sun on your skin, when you get a sunburn.
Thinning of the ozone layer allows more ultraviolet radiation to reach Earth’s surface. As a result, humans are exposed to more harmful UV radiation, which increases our risk of getting skin cancer.
Gamma rays need to be precisely directed at a tumour so that the gamma rays only kill harmful cancer cells, not other healthy body cells.