P5.2 Flashcards
Do these + Check if you understand this first
Describe the difference between a longitudinal and transverse wave
In a longitudinal wave, oscillations occur parallel to the direction of energy transfer.
In a transverse wave, oscillations occur perpendicular to the direction of energy transfer.
What is EM radiation
- light waves
- travels as a wave
Can EM radiation travel in a vacuum
YES
Is EM radiation transverse or longitudinal
Transverse
Do EM waves require particles to travel
NO - that’s why it can travel in a vacuum
What determines the ‘colour’ of a light wave
It’s frequency / wavelength
What do you need to produce any sort of wave
Something must initially oscillate / vibrate
How are sound / mechanical waves created
Are created by vibrating particles
….. Which collide with neighbouring particles…
… transferring kinetic energy
How are EM waves created
Are created by vibrating charged particles!!
… which creates an oscillating electrostatic field.
…. Which creates an oscillating magnetic field
… transferring electromagnetic energy
Define the EM spectrum
A Continuous range of all possible frequencies/ wavelengths of EM radiation
Small wavelengths has…
High frequency’s
Large wavelengths has..
Low frequency’s
As wavelength increases…
Frequency decreases
What is the amplitude of EM radiation
A measure of its light intensity
Types of EM radiation = pneumonic
RADIO MICROWAVE INFRARED VISIBLE ULTRAVIOLET X-RAY GAMMA RAY
What EM radiation has the largest wavelength
Radio waves
What EM radiation has the smallest wavelength
Gamma rays
What EM radiation has the smallest frequency
Radio waves
What EM radiation has the highest frequency
Gamma rays
Low frequency means…
Low energy
Define light intensity
How much light is arriving in a given time over a given area
A distant star explodes and emits red light and gamma rays simultaneously.Explain why gamma rays and red light rays reach the Earth at the same time. (3 marks)
Gamma rays and red light rays are both forms of electromagnetic radiation.
Thus, both travel at the same speed in a given medium.
Hence, they will arrive at the Earth at the same time if emitted simultaneously.
How are radio waves produced - 5 steps
- An oscillating potential difference is applied across a wire.
- Electrons oscillate backwards and forwards at same frequency.
- Produces oscillating electrostatic and magnetic fields.
- These fields travel and cut across an aerial.
- Electrons inside the aerial oscillate, producing anelectrical signal.
What does the term ‘frequency of visible light’ mean
The frequency of EM waves in the visible part of the EM spectrum.The frequencies of light from red to blue
How to remember order of colours in EM spectrum
Richard of York Gave Battle in Vain = Red Orange Yellow Green Blue Indigo Violet
LARGE wavelength to SHORT wavelength
LOW frequency to HIGH frequency
Which colour has the largest wavelength
RED
Which colour has the shortest wavelength
Violet
Which colour has the highest frequency
Violet
Which colour has the lowest frequency
Red
If you were to wave/oscillate the balloon at a regular rate, you would give rise to charged particles oscillating at a given frequency.
Charged particles (electrons) have electrostatic fields around them.
Oscillating the balloon, produces oscillating electrostatic fields.
These oscillating electrostatic fields will produce oscillating B-fields, and the frequency of oscillation is low enough to match that of radio waves.
Penetration power + uses + hazards = visible light waves
Penetration power + uses + hazards = infrared
Penetration power + uses + hazards = micro waves
Penetration power + uses + hazards = radio waves
Penetration power + uses + hazards = ultraviolet
Penetration power + uses + hazards = X - Rays
Penetration power + uses + hazards = Gamma Rays
Explain why radiation can sterilise a syringe
Gamma radiation can be used to sterilise the needle.
Gamma will penetrate the plastic bag.
Gamma will then kill any bacteria/microorganisms that may be present on the needle.
Explain why some scientists think that using your mobile phone to make calls will effect your health
Mobile calls are transmitted using microwaves.Microwaves cause water to heat up.
Your brain contains a lot of water – you irradiate your brain with microwaves when making a call.
Blue light has a shorter wavelength than red light. (1)
Pits on a disc can be closer together when using blue light to read. (1)
Thus, blu-ray discs are able to store more information. (1)
How does infrared imaging work
A charge coupled device (CCD) absorbs the infrared radiation and displays it as visible colour.
Different colours of visible light are used to indicate the different intensities of infrared radiation.
The hotter a certain part of a medium,the more infrared light it will emit.
What do thermal imaging cameras produce
thermograms
What is a CCD
A charge coupled device (CCD) absorbs the infrared radiation and displays it as visible colour.
If an object is hotter, will it emit more or less infrared radiation
MORE
How do X - Rays work - summary
X-rays produce images by showing contrast(differences in shades) between different media.
How do x - rays work - steps
X-rays are used to irradiate a person’s body.
X-rays will pass through soft tissue (low density medium), but are absorbed by bone (high density medium).
X-rays that pass through the body, darken photographic film.
The film remains white where X-rays were absorbed by the body and didn’t reach the film. = BONE
How does Gamma imaging work
Radioactive tracers are ingested by/injected into a patient and quickly enter the bloodstream and organs.
The intensity of the gamma radiation being emitted is monitored outside by a camera.
Where there is poor blood flow inside the body, less gamma radiation will be emitted there, and this indicates possible health problem.
What is a radioactive tracer
a radioactive compound of an element.
Radioactive tracers will (usually) emit gamma radiation.
Explain why using infrared or gamma rays are different from using X-rays for medical imaging
X-rays are produced externally and then pass the through the body (either being transmitted or absorbed).
Infrared and Gamma are emitted from inside the body.
X-ray images are high resolution (show small details);infrared and Gamma images have poorer resolution images.
Explain the ways in which hospital staff reduce the potential damage to patients from the use of X-Ray and Gamma ray imaging
patients are limited to a certain number of X-ray and gamma ray images per year, to reduce their exposure to X-rays and gamma rays.
+ wear led aprons / shields
+ walls are lined with thick lead
Why are X-rays and gamma radiation dangerous
X-rays and gamma are dangerous to human health, as they are ionising radiation.
Why do you not need to take any precautions when using infrared radiation
they are too low in energy to be ionising.
The behaviour of an ultrasound wave when they meet a boundary is used to produce an image - explain how
Waves will partially reflect when they meet the boundary between two materials (as they change speed).
The time taken for the reflected waves to return to the transducer is then used to calculate the depth at which the boundary is present.
Why are x - rays able to produce detailed images
Because their wavelength is short
