P6 - Waves Flashcards
What do waves transfer from one place to another without transferring?
Energy
Waves transfer energy but not matter.
What is the amplitude of a wave?
The maximum displacement of a point on the wave from its undisturbed position.
Define wavelength in the context of waves.
The distance between the same point on two adjacent waves.
What is frequency measured in?
Hertz (Hz).
How many waves correspond to 1 Hz?
1 wave per second.
What type of waves have oscillations perpendicular to the direction of energy transfer?
Transverse waves.
Give three examples of transverse waves.
- All electromagnetic waves (e.g., light)
- Ripples and waves in water
- A wave on a string.
In longitudinal waves, how are the oscillations oriented?
Parallel to the direction of energy transfer.
What is an example of a longitudinal wave?
Sound waves in air.
What are mechanical waves?
Waves that require a medium to travel, such as water waves, shock waves, and waves in springs and ropes.
True or False: The speed of a wave is the speed at which matter is being transferred.
False.
What equipment is used to measure the speed of sound?
Oscilloscope and microphones
An oscilloscope displays the detected waves, while microphones capture the sound waves.
What is reflection in wave behavior?
Reflection occurs when an incoming ray is sent back away from the second material without being absorbed or transmitted.
This is the principle behind how echoes are created.
What are electromagnetic (EM) waves classified as?
EM waves are transverse waves.
They transfer energy from a source to an absorber.
Do all EM waves travel at the same speed in a vacuum?
Yes, all EM waves travel at the same speed through air or a vacuum.
They can travel at different speeds in different materials, which can lead to refraction.
How are electromagnetic waves grouped?
They are grouped based on their wavelength and frequency, forming a continuous spectrum.
There are seven basic types of EM waves.
What part of the EM spectrum can our eyes detect?
Our eyes can only detect visible light.
Why are different EM waves used for different purposes?
Different EM waves have varying properties that make them suitable for specific applications.
What is refraction?
Refraction is the change in direction of a wave when it crosses a boundary between two materials. (like a laser hitting glass and changing direction)
What occurs when a wave hits a boundary at an angle?
The wave changes direction and is refracted.
How does density affect wave speed?
Usually, the higher the density of a material, the slower a wave travels through it.
What is optical density?
Optical density is a measure of how quickly light can travel through a material; higher optical density means slower light travel.
What changes in a wave when it is refracted?
The wavelength of a wave changes, but the frequency stays the same.
What is the angle of incidence?
The angle of incidence is the angle between the incident ray and the normal.
What is the angle of refraction?
The angle of refraction is the angle between the refracted ray and the normal.
What happens to the refracted ray if the second material is optically denser?
The refracted ray bends towards the normal, and the angle of refraction is smaller than the angle of incidence.
What happens to the refracted ray if the second material is less optically dense?
The angle of refraction is larger than the angle of incidence.
Fill in the blank: The part of the wave front that travels slower is in the _______ material.
denser
Fill in the blank: The closer wave fronts indicate a change in _______ and velocity.
wavelength
What are radio waves?
Radio waves are electromagnetic (EM) radiation with wavelengths longer than about 10 cm.
How are electromagnetic waves made?
EM waves are made up of oscillating electric and magnetic fields.
What produces radio waves in an electrical circuit?
An alternating current (AC) produces radio waves in an electrical circuit.
What is the role of a transmitter?
A transmitter is the object in which charges oscillate to create radio waves.
What happens when radio waves reach a receiver?
The radio waves are absorbed, transferring energy to the electrons in the receiver.
What effect does the absorbed energy have on electrons in the receiver?
The energy causes the electrons to oscillate and generate an alternating current if part of a complete electrical circuit.
What is the relationship between the frequency of the radio wave and the alternating current generated?
The current has the same frequency as the radio wave that generated it.
What are the characteristics of long-wave radio?
Long-wave radio has wavelengths of 1 - 10 km and can be transmitted and received over long distances due to diffraction.
What allows long-wave radio signals to be received beyond the line of sight?
Long wavelengths diffract around the curved surface of the Earth and obstacles like hills.
What are short-wave radio signals and how are they transmitted?
Short-wave radio signals have wavelengths of about 10 m - 100 m and can be reflected from the ionosphere for long-distance transmission.
What technology uses short-wave radio waves?
Bluetooth® uses short-wave radio waves to send data over short distances between devices.
What is required for FM and TV signals to be received?
FM and TV signals must be in line of sight of the transmitter.
How do medium-wave signals behave?
Medium-wave signals can reflect from the ionosphere, depending on atmospheric conditions and time of day.
Fill in the blank: Radio waves are primarily used for _______.
communication
True or False: Short-wave radio signals can only be received if the transmitter and receiver are in direct line of sight.
False
What type of waves are used for communication to and from satellites?
Microwaves
Microwaves can pass easily through the Earth’s watery atmosphere.
How does a satellite TV signal reach a satellite?
The signal is transmitted into space from a transmitter
This signal is picked up by the satellite receiver dish orbiting above Earth.
What happens to the satellite TV signal after it is picked up by the satellite?
The satellite transmits the signal back to Earth in a different direction
This signal is received by a satellite dish on the ground.
What causes a slight time delay in satellite communication?
The long distance the signal has to travel
This delay is noticeable between the signal being sent and received.
How do microwave ovens cook food?
Microwaves are absorbed by water molecules in food
This absorption causes the water to heat up and transfer energy to the rest of the food.
How deep can microwaves penetrate food in a microwave oven?
Up to a few centimetres
This penetration allows for even cooking as the energy is absorbed.
What type of radiation is given out by all objects?
Infrared (IR) radiation
The amount of IR radiation emitted increases with the object’s temperature.
What equipment can detect infrared radiation?
Infrared cameras
These cameras convert IR radiation into an electrical signal displayed on a screen.
What does the brightness of an object in an infrared camera indicate?
The hotter an object is, the brighter it appears
This allows for temperature monitoring of objects.
How is food cooked using infrared radiation?
The temperature of the food increases when it absorbs IR radiation
An example is the heat from a toaster’s heating element.
How do electric heaters warm a room?
They emit infrared radiation when a current flows through a heated wire
The emitted IR radiation is absorbed by objects and air, causing an increase in temperature.
Fill in the blank: Absorbing IR radiation causes objects to get _______.
hotter
True or False: Infrared radiation can be used for monitoring temperature.
True
What type of waves are used for communication to and from satellites?
Microwaves
Microwaves can pass easily through the Earth’s watery atmosphere.
How does a satellite TV signal reach a satellite?
The signal is transmitted into space from a transmitter
This signal is picked up by the satellite receiver dish orbiting above Earth.
What happens to the satellite TV signal after it is picked up by the satellite?
The satellite transmits the signal back to Earth in a different direction
This signal is received by a satellite dish on the ground.
What causes a slight time delay in satellite communication?
The long distance the signal has to travel
This delay is noticeable between the signal being sent and received.
How do microwave ovens cook food?
Microwaves are absorbed by water molecules in food
This absorption causes the water to heat up and transfer energy to the rest of the food.
How deep can microwaves penetrate food in a microwave oven?
Up to a few centimetres
This penetration allows for even cooking as the energy is absorbed.
What type of radiation is given out by all objects?
Infrared (IR) radiation
The amount of IR radiation emitted increases with the object’s temperature.
What equipment can detect infrared radiation?
Infrared cameras
These cameras convert IR radiation into an electrical signal displayed on a screen.
What does the brightness of an object in an infrared camera indicate?
The hotter an object is, the brighter it appears
This allows for temperature monitoring of objects.
How is food cooked using infrared radiation?
The temperature of the food increases when it absorbs IR radiation
An example is the heat from a toaster’s heating element.
How do electric heaters warm a room?
They emit infrared radiation when a current flows through a heated wire
The emitted IR radiation is absorbed by objects and air, causing an increase in temperature.
Fill in the blank: Absorbing IR radiation causes objects to get _______.
hotter
True or False: Infrared radiation can be used for monitoring temperature.
True
What are optical fibres?
Thin glass or plastic fibres that carry data over long distances as pulses of visible light
They work based on the principle of reflection.
How do optical fibres transmit data?
Light rays are bounced back and forth until they reach the end of the fibre
This is due to the principle of total internal reflection.
Why is visible light used in optical fibres?
It is easy to refract light enough so that it remains in a narrow fibre
Additionally, light is not easily absorbed or scattered as it travels along a fibre.
What is fluorescence?
A property of certain chemicals where UV radiation is absorbed and visible light is emitted
This is why fluorescent colours appear so bright.
How do fluorescent lights work?
They generate UV radiation absorbed and re-emitted as visible light by a phosphor layer inside the bulb
They are energy-efficient and suitable for long-term use.
What is the purpose of security pens that use UV ink?
To mark property with a name that glows under UV light, aiding in identification if stolen
The ink is otherwise invisible to the naked eye.
What causes a suntan?
Exposure to ultraviolet radiation (UV) produced by the Sun
Tanning salons use UV lamps for artificial suntans.
What is the role of X-rays in hospitals?
To take ‘photographs’ of people to check for broken bones
X-rays easily pass through flesh but not through denser materials like bones.
What determines the X-ray image?
The amount of radiation absorbed by different materials
Denser materials absorb more radiation, resulting in a clearer image of bones.
How are X-rays and gamma rays used in cancer treatment?
They are used in radiotherapy to kill living cells, specifically targeting cancer cells
This is done to minimize damage to normal, healthy cells.
What is a medical tracer?
A gamma-emitting source injected into a patient to track its progress in the body
Gamma radiation is ideal for this as it can pass out through the body and be detected.
What precautions do radiographers take when using X-rays and gamma rays?
Wear lead aprons, stand behind lead screens, or leave the room to minimize exposure
Both types of radiation can be harmful to people.
What is a characteristic of low frequency electromagnetic waves?
Low frequency waves, like radio waves, don’t transfer much energy and mostly pass through soft tissue without being absorbed.
What types of electromagnetic waves are considered high frequency?
UV, X-rays, and gamma rays.
What are some serious effects of UV radiation exposure?
- Sunburn * Premature skin aging * Blindness * Increased risk of skin cancer
What are X-rays and gamma rays classified as?
Ionising radiation.
What can ionising radiation cause in living cells?
- Gene mutation * Cell destruction * Cancer
How is radiation risk measured?
Using the radiation dose in sieverts.
Why is it important to assess the benefits of high frequency electromagnetic radiation?
To determine if the benefits outweigh the health risks.
What is the relationship between the risk of developing cancer from an X-ray and the risk of not treating injuries from a car accident?
The risk of developing cancer from an X-ray is much smaller than the potential health risk of not finding and treating injuries.
What does the radiation dose in sieverts indicate?
The risk of harm from the body being exposed to radiation.
Is the radiation dose a measure of the total amount of radiation absorbed?
No, it is not a measure of the total amount of radiation absorbed.
What is the conversion between millisieverts and sieverts?
1000 mSv = 1 Sv.
Can radiation doses be calculated for different types of radiation?
Yes, for all types of radiation, not just UV, X-rays, and gamma rays.
When undergoing a CT scan, which part of the body receives a higher radiation dose?
The chest.
How much higher is the risk of gene damage from a chest CT scan compared to a head scan?
Four times higher.
Fill in the blank: A CT scan uses X-rays and a _______ to build up a picture of the inside of a patient’s body.
computer.
