P12 Flashcards
What are electromagnetic waves ?
They are electric and magnetic disturbances that can be used to transfer energy from a source to an absorber .
Do electromagnetic waves transfer matter ?
no
What is the electromagnetic spectrum in order from lowest energy and frequency to highest ?
- radio waves
- micro waves
- infared
- visible light
- ultra violet
- x rays
- gamma radiation
Do the wavelengths get shorter from radio waves to gamma rays ?
yes
At what speed do all electromagnetic waves travel at ?
3.0 x 10 to the power of 8 m/s
What is white light and why is it called this ?
White light is light from ordinary lamps and from the sun . It is called this because it contains all the colours on the spectrum .
Do all objects emit radiation ?
Yes
What is infared radiation ?
radiation from the sun that is absorbed by your skin . It can damage , burn , or kill skin cells .
What is an optical fibre ?
The technology that transmits information as light pulses along a glass or plastic fibre .
Why do optical fibres use infared radiation ?
Infared radiation is absorbed less that visible light in the glass fibres .
What three things can you use infared radiation for ?
- You can use infared radiation to detect tissue that is unhealthy .
- You can use it to see people in the dark .
- It is used to heat up objects quickly , like an electric heater .
What two things do people use micro waves for ?
- communication
- to heat up food faster
What are radio waves used for ?
Used to carry radio , TV and mobile signals .
Why can microwaves and radiowaves be hazardous ?
They penetrate peoples bodies and can heat internal parts of the body.
What is a leslie cube ?
A hollow metal box made up of copper or steel . The cube has different types of surfaces on the four faces .
What are usually the four faces on a leslie cube ?
A matt black surface , white surface , polished surface and an unpolished surface .
What is the independent variable in the leslie cube practical ?
The colour and reflectivity of each surface .
What is the dependent variable in the leslie cube practical ?
The temperature
What is the controlled variable ?
Volume of water and the distance between the thermometer and cube.
What is the equipment you need for the leslie cube practical ?
A cube , kettle , ruler , heat proof mat and an infared thermometer .
What is the method used for the leslie cube practical ?
- Pour hot water into the leslie cube until it is full .
- Use a ruler to measure 10 cm from one surface of the leslie cube .
- Use an infared thermometer to measure the temperature of the surface .
- Read the temperature and the colour reflectivity of the surface .
- Repeat for each of the different surfaces .
What is visible light used for ?
Used to form images in cameras and video cameras . Can also be used in surgery .
What is ultraviolet radiation used for ?
Used for crime evidence , forged banknotes , passports and driving licenses .
What is ultr
What are x-rays used for ?
Used to produce medical images of bones .
Why are x-rays used to look a broken bones ?
Because they can pass through the bodies tissues and absorbed by the bones .
What are gamma rays used for ?
Similar to x rays , however they sterilise food by killing bacteria and it can also treat cancer .
What do you call a wave carrying any type of signal ?
A carrier wave .
Give things a wavelength of a wave effects ?
How far they can travel
How much they spread
How much information they carry
What is an oscillator ?
A mechanical or electronic device produces a current .
How are ultraviolet rays harmful ?
They are harmful to the human eye and can cause blindness . They are also harmful to your skin .
What will stop a gamma or x ray getting to you ?
A thick plate of lead
What are two similarities between a gamma ray and x ray ?
They are both short wavelengthed and carry more energy
What two ways do gamma rays and x rays differ ?
X rays are produced when electrons or other particles moving at high speeds are stopped
Gamma rays can penetrate more subtances .
Can a gamma ray be used to remove a cancerous tumour ?
Yes
How are x-rays produced ?
They are produced in an x ray tube when fast moving electrons hit a target .
What is a contrast medium ?
This enables the internal surfaces in an organ to be seen on a radiograph
What are the three types of radiation that is emitted from radioactive substances ?
Alpha , beta and Gamma
What three things does a radiation dose depend on ?
- The type of radiation used
- How long the body is exposed to it
- The energy per second absorbed by the body from the radiation
What are radiation doses measured in ?
Measured in sieverts or milliserverts
