P6: Waves Flashcards
what are the two types of waves
transverse and longitudinal
define a transverse wave
A wave for which the oscillations are perpendicular to the direction of wave transfer
what is a longitudinal wave?
a wave for which the oscillations are parallel to the direction of energy transfer
Give two examples of transverse waves
- Electromagnetic waves
- Seismic s-waves
Give two examples of longitudinal waves
- Sound waves
- Seismic p-waves
What are the two parts of a longitudinal wave called?
- compressions and rarefractions
Define amplitude
- the maximum displacement of a point on a wave away from its undisturbed position.
What is the definition of wavelength?
The wavelength of a wave is the distance from a point on one wave to the equivalent point on the adjacent wave.
What is the definition of frequency? Give the unit
The frequency of a wave is the number of waves passing a point each second.
- Hertz , Hz
What is wave speed?
The wave speed is the speed at which the energy is transferred (or the wave moves) through the medium
What does a wave transfer?
energy
State the equation used to calculate wave speed. Give appropriate units.
Wave speed = frequency x wavelength
speed = m/s
frequency = Hz
Wavelength = m
What happens to waves at the boundary between materials?
They can be reflected, absorbed or transmitted.
How do sound waves travel through a solid?
- the particles in the solid vibrate and transfer kinetic energy through the material
What is the frequency range of human hearing?
20 Hz - 20kHz
What are ultrasound waves?
- waves which have a frequency higher than the upper limit of human hearing
- (20kHz)
Give an example use for ultrasound waves
- medical or industrial imaging
What natural event causes seismic waves to be produced? What types are produced?
- Earthquakes
- They produce both P-waves and S-waves
State a difference between the mediums that P-waves and S-waves can travel through
- P waves travel through both solids and liquids
- S-waves only travel through solids
What technique is used to detect objects in deep water and measure water depth and how?
- Echo sounding
- high frequency sound waves are emitted, reflected and detected
- time difference between emission and detection alongside wave speed, are used to calculate distances
What type of spectrum do electromagnetic waves form?
A continuous spectrum
order the types of electromagnetic radiation from lowest to highest frequency
- radio waves
- microwaves
- infrared
- visible light
- ultraviolet
- X-rays
- Gamma rays
How do the speeds of EM radiation differ in a vacuum and in air?
- EM waves all travel at the same speed in a vacuum and in air
What property of waves in different mediums causes refraction?
- velocity
- wave speed is slower in denser materials, causing refraction
In which direction ( relative to the normal) do waves refract when entering a denser medium?
- they bend towards the normal
- the angle of refraction is less than the angle of incidence
What type of waves can be produced by oscillations in an electrical circuit?
- Radiowaves
How can radio waves create an alternating current in a circuit?
- When radio waves are absorbed , they can induce oscillations of electrons in a circuit
- with the same frequency as the radiowaves themselves
- causing alternating current
Where do gamma rays originate from ?
- they orginate from changes in the nuclei of atoms
give two health effects caused by ultraviolet waves
- they can cause the skin to age prematurely
- this can increase the risk of developing skin cancer
give two health effects caused by x-rays and gamma rays
- they are ionising radiation so can cause mutations in genes
- they can lead to increased risk of developing various cancers
Give three practical uses for infrared radiation
- electrical heaters
- cooking food
- infrared cameras
Give two practical uses for microwave radiation
- Satellite communications
- Cooking food
Give two practical uses for radio waves
- television transmission
- radio transmission
What wave phenomenon is used by lenses to form an image
refraction
How does a convex lens form an image ?
- Parallel rays of light are refracted and brought together at a point known as the principal focus
What is meant by the focal length of a lens?
- the distance from the lens to the principal focus
What is the difference between the image produced by a convex and a concave lens?
- convex lenses can produce real or virtual images
- concave lenses can only produce virtual images
Why does magnification not have a unit
- it is the ratio between image height and object height
- ratios do not require units
what symbol is used to represent a convex lens in a ray diagram?
↕
what symbol is used to represent a concave lens in a ray diagram?
🞃
|
🞁
what determines the colour of visible light waves?
the wavelength and frequency of the light waves
What colour of visible light has the highest frequency? What colour of visible light has the largest wavelength?
- blue
- red
What is a specular reflection?
- Reflection that happens when parallel waves are reflected in a single direction by a smooth surface
- produces an image
What is a diffuse reflection?
- Reflection that happens when parallel waves are reflected by a rough surface and the reflected rays are scattered in lots of different directions
- this does not produce an image
How does a red colour filter work?
- a red filter absorbs all wavelength of light other than those in the red range of the spectrum
- this means only red light passes through the filter
What determines the colour of an opaque object?
- different objects reflect different wavelengths of light by different amount
- the wavelengths that are most strongly reflected determine the colour
What happens to the wavelengths of light that aren’t reflected by an opaque object?
- any wavelengths that aren’t reflected are absorbed by the object
What colour does an object appear if all wavelengths are reflected by equal amounts>
white
What colour does an object appear if all wavelengths are absorbed?
- black
what is radiation dose?
Radiation dose is a measure of the risk of harm resulting from an
exposure of the body to the radiation
Why do bananas appear yellow?
Bananas absorb all wavelengths of light
except the yellow part of the visible
spectrum which is reflected
Explain why a piece of paper
appears white (2)
- All of the wavelengths of visible light are reflected from its surface.
- They combine together and produce white light
What happens if you view a blue
object with a blue filter?
● Blue light is reflected by blue object
● Blue filter transmits blue light and
absorbs all other wavelengths
So object looks blue
. What happens if you view a red
object with a blue filter?
● Red light is reflected by red object
● Blue filter will absorb red light
● So object appears black
What are transparent objects?
● Objects that transmit light
● In straight lines
What are translucent objects?
● Objects that transmit light
● But can also scatter it so you cannot see
clearly through them
What provides evidence that
the S-waves do not travel
through the outer core?
The S wave shadow zone
What does the S wave shadow zone tell us about the outer core?
The outer core is liquid as S waves cannot travel through liquids
Why do both waves change
direction as they go deeper into
the Earth?
The density of the Earth changes – this causes
the waves to change speed and refract
what do all bodies (objects) emit and absorb?
infrared radiation
what hat happens to the quantity of infrared radiation emitted by an object as temperature increases?
the hotter the object, the more infrared radiation it will emit
What is a perfect black body?
An object that absorbs all of the radiation that is incident upon it
How much radiation does a perfect black body reflect or transmit?
None.
Why is a perfect black body the best possible emitter of radiation?
- it is a perfect absorber since it absorbs all radiation incident upon it
- a perfect absorber is also a perfect emitter
What can be said about the rates of emission and absorption for a body at constant temperature?
The body is absorbing and emitting radiation at the same rate
what can be said about the rates of emission and absorption for a body increasing in temperature?
the body is absorbing radiation faster than it is emitting it
Give two factors that affect the temperature of the Earth?
- The Earth’s rate of absorption and emission of radiation
- the amount of reflection of radiation into space
Explain why a mug of hot
chocolate will get cold after 1
hour
● The hot chocolate is initially hotter than
the surroundings
● Therefore it will emit more infrared
radiation than it absorbs
● So its temperature decreases
- Explain why the surface
temperature of the Earth increases during the day
● During the day the sun is shining
● More infrared radiation will be absorbed
by the surface of the Earth than emitted
. Explain why the surface
temperature of the Earth
decreases during the nigh
● During the night, there is less infrared
radiation absorbed by the surface of the
Earth than emitted
.What type of surfaces are best and worst
at absorbing and emitting
infrared radiation?
best : Black matt surfaces
worst: white shiny surfaces
Why are light, shiny blankets
used to keep people warm?
● A light shiny outer surface emits a lot
less radiation than dark/matt surfaces
● The person will be kept warm as the
infrared radiation emitted is reduced
what is the exception to the refraction rule
- if waves enter or leave the medium along the normal ( at right angles to the surface)
- they do not change direction
what happens when electromagnetic waves are absorbed !
- it causes changes to atoms eg causing electrons to change energy levels
- these changes can result in EM waves being generated and absorbed over a wide frequency range
Describe the image shown when an object is more than 2 focal lengths from the convex lens
- diminished
- inverted
- real
describe the image shown when an object is between 1 and 2 focal lengths from the convex lens
- magnified
- Inverted
- Real
describe the image shown when an object is less than one focal length between the convex lens
- magnified
- upright
- virtual
Describe the image shown from an object with a a concave lens
- diminished
- upright
- virtual
What is white light and what happens when it is passed through a prism
- a mixture of all the different colours
- it splits into a spectrum : red orange yellow green blue indigo violet
