Waves Flashcards
What do waves transfer?
energy
How do waves travel from one place to another?
they oscillate
What is the max height of the wave called?
amplitude
What is the wavelength?
one entire oscillation
What are the 2 ways to work out frequency?
1/time period
wavespeed/wavelength
How do you work out time period?
1/frequency
How do you work out wavespeed?
frequency*wavelength
what greek letter represents wavelength?
Lamda (λ)
What direction are oscillations in transverse and longitudinal?
perpendicular to the direction of energy transfer (T)
parallel to the direction of energy transfer (L)
Example of transverse waves?
EM waves
Examples of longitudinal waves?
sound, seismic waves
What 3 things can happen when a wave hits a surface?
absorption, transmission, reflection
In reflection, which 2 angles are always equal?
angle of incidence = angle of reflection
What is the normal?
a dashed line that is perpendicular to the surface
What is the point of incidence?
the point where the incident ray touches the surface
What is specular reflection?
when the boundary is flat, so the waves reflects in the same direction
What is diffuse reflection?
The boundary is bumpy, so the waves reflect in all different direction (because the normal is at different angles)
What type of image will specular reflection produce?
a clear image
why do waves travel at different speeds through different mediums?
different mediums have different density
What is refraction?
a wave changing direction when passing from one medium into another
Which way will the wave bend when it enter a denser medium?
towards the normal
Which way will the wave bend when it enter a less dense medium?
away from the normal
What is the difference between the frequency and wavelength of a wave when it enters another medium?
if the wave speeds up the wavelength increase and the frequency stays the same (vice versa)
What is the order of the EM spectrum from most ionising to least?
gamma rays, x-rays, uv rays, visible light, infrared, microwaves, radio waves
What 3 things are the same about all EM waves?
they are all transverse
they all travel at 3x10^8 m/s in a vacuum
they all can travel through a vacuum
what is the range of wavelengths for EM waves?
10^4m to 10^-15m
What are the 2 types of lenses?
convex (convergent) and concave (divergent)
What does a convex lens look like and what does it do to light rays?
it has a bulge in the middle and curves to meet at corners at the top and bottom. It causes light rays to refract inwards and converge on a point.
What does a concave lens look like and what does it do to light rays?
it is wider on the top and bottom and thin in the middle. It causes light rays to refract outwards so they spread out (diverge).
how many principle focuses do lenses have?
2, 1 on each side
What is the principle axis?
the line running through the centre of the lens where no refraction occurs.
What is the focal length?
the distance between the centre of the lens and the principle focus
How does focal length relate to the power of the lens?
the shorter the focal length, the more powerful the lens
What does a more powerful lens mean?
it refracts light more strongly
How do you make a lens more powerful?
make the lens more curved or make it out of a material that naturally refracts light more strongly
Where are images formed?
where all the light rays from a particular point on an object, appear to come together
What is the difference between a real and virtual image?
Real:
light rays actually come together to form image.
image can be captured on the screen
Virtual:
Light rays dont actually come together where the image appears to be.
Cannot be projected on to a screen.
What is an example of a virtual image?
reflection in a mirror
Give 3 examples of uses of ultrasound.
industrial imaging
pre natal scanning
sonar
What is ultrasound?
sound that vibrates at frequencies over 20,000Hz
What is the range of human hearing?
20-20,000Hz
What happens when ultrasound hits the boundary between mediums?
some of it is reflected and some is refracted.
How does ultrasound work?
when the ultrasound waves are fired at an object, some pass through and some are reflected. The same happens every time the waves hit a boundary within the object. If we know the speed of the wave and the time it takes to be reflected, we are able to understand the different layers and boundaries within the object.
Is ultrasound harmful?
no.
What are the 3 types of seismic waves?
P, S and L
What are 3 differences between p and s waves?
p waves are longitudinal and faster and can travel through solids and liquids,
s waves are transvers and slower and can travel through only solids
What device is used to detect seismic waves?
seismometers
Why do the waves curve whilst travelling through the mantle and outer core?
the mantle and outer core having varying densities, causing the waves to refract slightly every time, making them curve
Can s waves travel through the outer core?
no.
What is the shadow zone?
the area of the earth where no waves reach
What causes the shadow zone?
the refraction of the waves
What 3 things helped prove the existence of a liquid outer core?
no s waves were detected opposite the epicentre
p waves were refracted
shadow zone
Which of types of electromagnetic waves can be used in communication?
Microwaves
Radio waves
How can radio waves be created?
using an alternating current
What 2 things are microwaves used for?
satellite communication and microwave ovens
Why are radio waves not used for satellite communication?
they are reflected by the atmosphere
What are optical fibres used for?
used to transmit data really quickly over very large distances (halfway around the earth)
What can UV rays be used for?
Check for ‘invisible markings’ on passports
Give sun tans
Destroy microorganisms in water sterilisation
What can infrared radiation be used for?
cooking and night vision
What can visible light be used for?
optical fibres, seeing
What is fluorescence?
Ultraviolet light energy being absorbed and re-emitted as visible light
What are X-rays used for?
to view the internal structure of objects, e.g. medical imaging
How do we use X-rays to find broken bones?
X-rays are fired at the patient
X-rays are absorbed by materials which are very dense, like bones.
X-rays are transmitted through materials which are not very dense, like lungs and intestines.
The X-rays that pass through are detected by a detector plate to form an X-ray image
Are X-rays absorbed or reflected by bones?
absorbed
In hospitals what are gamma rays used for?
Perform medical imaging
sterilising medical equipment and food
Treat cancer
A green glass bottle appears green because:
The bottle reflects and/or transmits green light and absorbs other colours of light.
What colours does a blue filter transmit?
blue
What colours does a yellow filter transmit?
red, green and yellow
What colours does an indigo filter transmit?
red, blue, indigo
What happens to the wavelength of radiation emitted by an object if its temperature increases?
decreases
What happens when sound waves travel from a less dense medium, to a more dense medium?
speed increases
