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Physics > P5 > Flashcards

P5 Flashcards

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1
Q

What are waves?

A

An oscillation that transfers energy

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2
Q

What are sound waves?

A

Vibrations of waves
From vocal chords

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3
Q

What are mechanical waves?

A

Sound and water waves
Need a medium (matter) to travel through

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4
Q

What are electromagnetic waves?

A

Used to communicate between the two phones
Doesn’t need a medium

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5
Q

What are longitudinal waves?

A

The direction of vibration of individual air molecules is the same as the direction of the wave

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6
Q

What are transverse waves

A

The direction of vibration is at right angles to the direction of the travel of the wave
Energy is transferred horizontally

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7
Q

What is the amplitude (A)?

A

Distance from the middle to the top (crest) or bottom (trough) of the wave

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8
Q

What is the wavelength (lambda)?

A

Distance from one point on a wave to the same point on the next wave

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9
Q

What is the frequency (F)?

A

Number of waves, or oscillations per second
Measured in hertz

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10
Q

What is the time period (T)?

A

The time for one wave to pass a given point

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11
Q

How do you show time period and wavelength?

A

On a displacement/time graph the time period is the distance from on point of the wave to the next point
On a displacement/distance graph the wavelength is that

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12
Q

How can you model transverse waves?

A

Ripples in water waves

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13
Q

How do you calculate wave velocity?

A

Wave velocity = frequency (Hz) x wavelength (m)

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14
Q

What are ways to measure the velocity of sound?

A

Time how long it takes to hear an echo of a clap when you’re at a distance from a wall
You can also connect a pair microphones a certain distance apart to an oscilloscope
Sound is longitudinal so any transverse wave is just the variation of pressure

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15
Q

What is refraction?

A

When a wave travels from one medium to another its velocity can change and so can it’s direction
Frequency stays the same but velocity and wavelength change

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16
Q

What 3 things happen to a wave when it hits the boundary between two medium?

A
  • reflected
  • transmitted
  • absorbed
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17
Q

What is ultrasound?

A

Sound of frequency greater than 20 000Hz
Cannot head it but other animals can
Ultrasound is useful as it has a very small wavelength so it can be focused into a beam

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18
Q

How is ultrasound used to create an image of a fetus?

A

1) transmitter beams ultrasound waves into mother
2) waves reflect from the different boundaries
3) machine calculates the distances using time and velocity and uses those to create an image
Method can also be used to find kidney stones, monitor blood flow, find depth of water
Echo sounding and sonar (used by submarines and fisherman)

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19
Q

Where happens to a sound wave when it hits a solid?

A

The sound reflects of different surfaces so an echo is heard until the sound is eventually absorbed
This makes the particles in the wall vibrate and the wall gets hotter

20
Q

What is the ear designed to do?

A

Detect, amplify and convert sound to an electric signal

21
Q

How does the ear work?

A

1) The outer ear (pinna and auditory canal) gathers and directs the sound into the ear drum, which vibrates
2) As the ear drum vibrates, it causes the ossicles to vibrate
3) They act like small levers that amplify the vibrations and pass them into the inner ear through the oval window
4) the cochlea has fluid in it which transmits the sound to small hairs which vibrate and produce electrical signals down the auditory nerve to the brain
5) shorter hairs resonate at higher frequencies so when you get holder you lose them and can’t hear higher pitched sounds

22
Q

What is resonance?

A

When you apply a vibration to an object at its natural frequency it’ll vibrate with a big amplitude

23
Q

What is a spectrum?

A

When you can identify the main items but they merge together with no gaps
Rainbow

24
Q

Which spectrum is white light apart of?

A

Electromagnetic spectrum

25
Q

What is the order of the E-M spectrum?

A

HIGHEST wavelength / LOWEST frequency
Radio waves
Micro waves
Infrared
Visible light
Ultraviolet
X-rays
Gamma rays
LOWEST wavelength / HIGHEST frequensy

26
Q

What are electromagnetic waves?

A

Consist of oscillating electric and magnetic fields
Fields oscillate at 90 degrees to the direction of the wave
All E-M waves travel through a vaccum at 3 x 10^8 (speed of light which is part of the e-m spectrum)

27
Q

Where to e-m waves transfer energy from and to?

A

Energy from sources (Sun, microwave oven) to absorbers (skin)

28
Q

How are radio waves produced and detected?

A

Produced in radio transmitters by an oscillating p.d across a wire which causes electrons to move backwards and forwards, producing a changing electric and magnetic field which are emitted as radio waves
When the fields meet another piece of metal (aerial) the electrons move which produces and electrical signal

29
Q

What are the applications of e-m waves?

A

Radio waves - TV & radio
Micro waves - Mobile phones, satellite communications, WI-FI & blue tooth, microwave oven for heating food
Infrared - TV remote, cooking food in grill or oven, thermal imaging
Visible - flashlight
Ultraviolet - killing bacteria in water
X - rays - X ray imaging, killing skin cancer cells
Gamma - kill cancer cell, with radioactive tracers to image internal organs like the liver and kidney

30
Q

What are the dangers of the higher frequency waves?

A

Ultraviolet - damage to DNA in the cells of your skin, cells can grow very quickly and cause cancer. Exposure of eyes to ultraviolet can cause development of cataracts which make your corneas cloudy
IONISING:
X - rays - damage cells and cause cancer
Gamma rays - damage or kill cells in the body

31
Q

How are infra red waves used for medical imaging?

A

Thermal imaging camera produces an image called a thermogram that shows regions of different temperatures
Can show problems with blood flow in blood vessels
Pixels inside a CCD (charge coupled device) absorb infrared and produce an image, the colours are added by a computer

32
Q

How are x rays used for medical imaging?

A
  • Can show broken bones as bones absorb X-rays but soft tissues such as skin and muscles do not
    Photographic film darkens when it absorbs X -crays and shows the detail of the internal structure of a human
  • A CCD can also detect X-rays, the coloursnshow differences in intensity due to the different densities of the materials that the X-rays have travelled through. Higher density materials absorb more X-rays
  • CT scans produce an image like a slice through your body
33
Q

How are gamma rays used for medical imaging?

A

Used as tracers to treat problems with organs like the kidneys
Doctor injects patient with a radioactive substance that emits gamma rays, called a tracer and the patients kidney absorbs the tracer
Doctor can diagnose the problem with a CCD image

34
Q

What do Ray diagrams show?

A

What happens when electromagnetic waves hit a surface or travel through matter

35
Q

How do you construct a ray diagram?

A
  • draw lines to represent the rays
  • draw a normal at 90 to the surface at the point where the ray hits it
  • measure the angles from the normal to the rays
36
Q

Why do e-m waves refract?

A

When they change speed
When the wave foes to a denser medium (air to glass) it slows down, goes towards the normal
The incident Ray is larger than the refracted ray

37
Q

What materials transmit e-m waves?

A

Walls transmit radio and micro waves but absorb visible light and ultraviolet
Plastic of a bin bag transmits infrared but absorbs visible light
Atmosphere absorbs X-rays and there are no natural sources of X-rays
Gamma rays from the sun and space are absorbed by the atmosphere but gamma rays from rocks could be in your home

38
Q

What is a convex lens?

A

Converging lens
In a magnifying lens
Refracts rays to a focal point or principal focus
When the rays are going into the lens parallel, the distance from the optical centre of the lens to the principal focus is called the focal length

39
Q

What is a concave lens?

A

Diverges the rays
Anything with a concave lens cannot be set on fire

40
Q

How to draw a day diagram to predict where the image of a lens is?

A

1) draw a day from the top of the onjectnto the lens parallel to the principal axis and from the lens through the focal point
2) draw a ray from the top of the object through the centre of the lens
3) where the two days cross (for real image), or appear to come from (for a virtual image)is the top of the image
4) the bottom of the object is on the principal,axis

41
Q

What are the 3 descirptions of the image?

A

Real or virtual
Upright or inverted
Magnified or diminished

42
Q

What is dispersion?

A

As each frequency of light travels at slightly different speeds and each frequency is refracted by a different amount
Colours with higher frequencies are refracted more
The spectrum of white light therefore spreads out which is dispersion

43
Q

What is perceived colour?

A

As the cones in the retina are only sensitive to red, green and blue, the brain combines the signals that are triggered from the 3 colours to make perceived colour

44
Q

What does a red filter absorb and transmit?

A

Absorbs all the frequencies of white light except red light
If a green light is passed through a red filter no light is transmitted so appears black

45
Q

What is specular reflection?

A

Gives a sharp image
Flatter surface

46
Q

What is diffuse reflection?

A

Not sharp
Textured surface
Reflected rays go in different directions

Physics (9 decks)

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