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Flashcards in Waves Pt2 Deck (23)
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1
Q

Visible light

A

Have a very large range
Violets at 400nm
Reds at 700nm
Can mix to make other colours other than rgb (primary)

2
Q

Opaque objects

A

Do not transmit light
Colour depends on which wavelengths are most strongly reflected
White reflect all equally, black absorb all
Transparent and translucent do transmit, some wavelengths may on,y be absorbed or reflected by these

3
Q

Filters

A

Only transmit certain wavelengths
Primary colour filter only transmits that colour
Filters that aren’t primary allow that colour and the colour that make it

4
Q

Colour mixing

A

Green plus blue to cyan
Blue plus red to magenta
Red plus green to yellow

5
Q

What surfaces absorb and emit better

A

Black over white

Matt over shiny

6
Q

Perfect Black body

A

Doesn’t exist
An object that absorbs all radiation that hits it
Intensity and distribution of wavelengths emitted depend on temp
As it increases intensity of emitted wavelengths increases
Increases more for short wavelengths to cause the peak wavelength to decrease

7
Q

How does radiation affect the earth’s temperature

A

During the day lots is transmitted to earth and is absorbed
At night less is absorbed than is being emitted
Overall it stays fairly consistent
Atmosphere changes affect overall temperature if it starts to absorb more

8
Q

Sound waves

A

Caused by vibrating objects which are passed in compressions and rarefractions
Travels fastest in solids
Can’t travel in space as vacuum
May hear in ear drum

9
Q

The ear

A

Sound waves causes the ear drum to vibrate
Passed on to ting bones ossicles through canals to the cochlea
Turns them into electrical signals for the brain to sense
Humans hear 20Hz-20kHz

10
Q

Sound waves reflection and refraction

A

Reflected by hard flat surfaces (Echoes)

Refract as they enter different media

11
Q

Ultrasound

A

Sounds over 20kHz ( we can’t hear)
Partially reflected as some is always reflected back, time it takes to reach a detector tells us how far away a boundary is

12
Q

Ultrasound medical imaging

A

Pass through the body but some is reflected at a boundary between media and is detected
Exact timing is processed
E.g. foetus-womb

13
Q

Ultrasound industrial imaging

A

Can be used to find flaws in pipes or materials
Reflected by the fat side
If there is a flaw it will be reflected sooner

14
Q

Seismic waves

A

If there is an earthquake seismic waves travel through the earth, detected using seismometers
Seismologists work out where the earthquake was based on time taken to reach and where it didn’t reach
Some are absorbed and some refracted at boundaries in the earth, most change speed slowly for a curve but some quick for a kink

15
Q

Types of seismic waves

A

P-waves and S-waves
P-waves travel through core and are detected at top sides and bottom to tell us where it is
S-waves only the top sides
P-waves longitudinal, travel through solids and liquids, faster
S-waves transverse, only through solids and slower

16
Q

Superposition of waves

A

If two waves meet at the same point, they briefly superpose to appear as one wave

17
Q

Constructive interference

A

When the combined amplitude is larger than the amplitude of the individual waves

18
Q

Destructive interference

A

When the amplitude of the combined wave is smaller than those of the individual waves

19
Q

Diffraction

A

Waves spread out when they pass through a gap so they may curve at the edges or be fully curved depending on the gap they have

20
Q

Diffraction through a gap wider than wavelength

A

Little diffraction, waves still pretty much straight. Forms a diffracted pattern of bright areas and dark patches.

21
Q

Gap a bit wider than wavelength, diffraction

A

Small diffraction at the edges but the middle is straight. Forms a diffracted pattern of bright areas and dark patches.

22
Q

Diffraction with gap the size of wavelength

A

The waves are semi-circles from the line increasing in size as you move away. Forms a diffracted pattern of bright areas and dark patches. Maximum diffraction.

23
Q

Snell’s law

A

Refractive index (n) = sin i / sin r

i = angle of incidence
r = angle of refraction