Unit 3 - Lesson 3: Uses and Dangers of EM Radiation Flashcards
Is ionising radiation dangerous?
Yes
The higher the frequency of an EM wave, the more harmful it is to humans. True or false?
True.
Which EM radiation does not follow this rule (i.e. which EM radiation isn’t more harmful to humans the higher the frequency)?
Visible Light
Which EM radiation is the safest? Why?
Radio waves because they are not absorbed by the body.
What does it mean when radiation is ionising? What can ionising radiation cause in humans?
When waves can remove electrons from the outer shell of an atom, we say they are ionising. Ionising radiation is very dangerous. It causes cancer and even death.
What are the uses of radio waves? How do radio waves work?
How do short wave radio waves work?
How do long wave radio waves work?
How do very short wave radio waves work?
What are their wavelengths?
Do they bend? Are they reflected? Is a transmitter needed?
Long distance broadcasting (radio and TV) and other communication.
Short wave radio waves (wavelength: 10-100m) travel long distances because they can be reflected between the Earth’s surface and atmosphere (ionosphere).
Long wave radio waves have a large wavelength (1-10km) so they can bend around the Earth.
Very short wave radio has small wavelengths (10cm-10m). They must be in direct site of the transmitter as they’re not reflected or bent. A transmitter emits radio waves and aerials receive them. The car radio converts the radio waves into sound waves.
What is the wavelength of short wave radio waves? How can they travel long distances?
Wavelength: 10-100m
They can travel long distances because they can be reflected between the Earth’s surface and atmosphere (ionosphere).
What is the wavelength of long wave radio waves? How can they travel?
Wavelength: 1-10km
They travel by bending around the Earth.
What is the wavelength of very short wave radio waves? How can they travel?
Wavelength: 10cm-10m
They travel by being in direct site of the transmitter as they’re not reflected or bent. A transmitter emits radio waves and aerials receive them. The car radio converts the radio waves into sound waves.
What are the harms of radio waves?
Radio waves are not harmful.
What are the uses of microwaves?
Cooking (with a microwave oven).
Communication via artificial satellites and radar.
How do microwaves enable humans to cook (with a microwave oven)? What are the harms of microwave ovens?
Water molecules inside food absorb microwaves. This makes them vibrate and get very hot. Food cooks evenly rather than on the surface like in a conventional oven or grill.
The harm of microwaves is that they heat human tissue (internal). However, microwave ovens have metal screens to protect users.
How do microwaves enable communication via artificial satellites and radar?
How can we measure the distance of an airplane from an observer involving microwaves?
Microwaves are good for satellite communication because they easily pass through the Earth’s atmosphere and objects. A mobile phone’s signals are sent by microwaves to a satellite. The microwaves are then sent to the recipient’s phone (or other satellites first if the journey is long).
Microwaves (and radio waves) can be used for radar. When they reflect off an object, they provide information about it. For example, its velocity or position (angle and distance).
We can measure the distance of an airplane from an observer by measuring the time it takes for the wave to reach and return from the plane. Use S = D/T rearranged and then half the distance.
What are the uses of infrared (IR)?
Heating.
Night Vision Equipment.
Short-Range Communication (like Remote Controls).
Do all objects emit infrared radiation? If an object gets hotter, will the object emit more or less infrared radiation?
Give two examples of objects that emit infrared.
All objects (including humans) emit infrared radiation. The hotter an object, the more it emits.
Radiators and fires emit infrared.
What does night vision equipment do regarding infrared? How can this aid policework?
Night vision equipment detects infrared. It detects the infrared (heat) off a human with no visible light. The hotter an object, the brighter it appears. Police helicopters use this to find criminals.
How can infrared be used for short-range communications?
Infrared carries signals from a remote control to a TV or other device. The radiation has a low penetrating power, meaning it works over short distances, unaffecting other signals.
What are the harms of infrared radiation?
Excessive infrared radiation can cause skin burns so wearing protective material is advised.
What are the uses of visible light?
Photography.
Optical Fibres.
Lasers (to read barcodes/DVDs)
How does visible light enable photography?
Light enters a camera lens. This focuses (directs) the light on to a film or sensor. An aperture controls how much light enters. The shutter speed determines how long the film or sensor is exposed to the light.
How does visible light enable optical fibres? What are optical fibres? How can this method aid surgery?
Optical fibres are an alternative to standard electrical wiring e.g. fibre optic internet.
Light is directed into a tube at such an angle that it cannot escape (total internal reflection). The same principle is used in endoscopes to see inside a patient’s body through either keyhole surgery (surgery through a small hole) or without an incision (e.g. through the mouth). This improves patient recovery time.
How does visible light enable lasers (to read barcodes/DVDs)?
Lasers of visible light can be used to read DVDs and compact discs. They can also read barcodes at the shop till.
What are the harms of visible light?
Visible light at high intensity can damage eyes.
What are the uses of ultraviolet (UV)?
Fluorescent lighting.
Security.
How does ultraviolet (UV) enable fluorescent lighting?
Fluorescent lamps are filled with mercury, neon or argon, which emits UV rays when a current is passed through. The tube is coated in fluorescence. This absorbs UV rays and emits visible light.
How does ultraviolet (UV) enable security?
We use chemicals that glow (fluoresce) under UV light on bank notes. If they shine under UV light, we know they’re real.
Security marker pens use the same process. The writing is shown under UV, but not visible light.
What are the harms of ultraviolet (UV)?
The sun emits UV rays, which give you a tan. Some consider this a positive use of UV.
Over exposure to UV rays can damage eyes (possible blindness and cataracts) and burn skin (sun burn). It can also lead to skin cancer.
The ozone layer prevents excessive UV rays reaching the Earth’s surface. Rising greenhouse gases have damaged the ozone layer, letting in more UV. This may have contributed to the rising number of skin cancer cases. Evidence suggests the ozone layer is healing, which may lower cases.
What are the uses of X-Rays?
Allow us to observe the internal structure of objects.
How can X-Rays allow us to observe the internal structure of objects?
X-rays can check for faults in machinery and buildings or view inside suitcases at the airport. As X-rays pass through soft body tissue, but not bones, we can use them to diagnose broken bones. X-ray machines work by aiming the x-rays through the body at a detector plate behind. An image appears on the plate. Bones will show whiter.
What are the harms of X-Rays?
X-rays can cause cell mutation, which can lead to cancer. Lead screens and aprons can protect other areas of the body and other people nearby during an X-ray bone scan.
What are the uses of Gamma Rays?
Sterilising food or medical equipment.
Treating Cancer.
How can gamma rays help sterilise food or medical equipment?
Gamma rays kill bacteria that could cause infection. They have very high energy, so they can pass through objects. This is good for sterilising objects sealed in a package. This increases the shelf life of food.
How can gamma rays help treat cancer?
Radiotherapy directs a large dose of gamma rays at a cancerous growth to kill cancer cells.
What are the harms of gamma rays?
Gamma rays can cause cell mutation.
They can cause cancer as well as treat it. During radiotherapy, the gamma rays are concentrated into a precise area to minimise the loss of healthy cells.
Lead screens and aprons can protect other areas of the body and other people nearby.
