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Physics > Waves > Flashcards

Waves Flashcards

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1
Q

Longitudinal waves

A

Movement of particles are parallel to the direction of energy

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2
Q

Transverse waves

A

Movement of particles are perpendicular to the direction of energy

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3
Q

Evidence that shows for ripples, it’s the wave that travels and not the water itself

A

A boat or piece of paper bobs up and down but does not move along with the wave

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4
Q

Amplitude

A

The maximum displacement from the rest line to the peak

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5
Q

Wavelength

A

The distance from a point in one wave to the equivalent point in the adjacent wave

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6
Q

Frequency

A

The number of waves passing a point each second

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7
Q

Describe an experiment to determine the speed of sound

A
  1. Two people stand distance of 100m apart measured using a trundle wheel
  2. One person has 2 wooden blocks which they bang above their head
  3. The second person has a stopwatch which they start when they see the first person bang the blocks and stop when they hear the sound
  4. This is then related several times and a mean is calculated
  5. The speed of sound is calculated using v=s/t
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8
Q

Describe a method to measure the speed of ripples on a water surface

A
  1. Full a rectangular tank with water
  2. On one side mark a starting point where the ripples will be generated
  3. Gently drop the small floating object into the water at the starting point which will create ripples
  4. As soon as the object is dropped start a stopwatch
  5. As the ripples expand outward use a rule to measure the distance from the starting point to where the ripples are at a certain point in time
  6. Stop the timer when the ripples reach a desired distance
  7. Calculate speed using v=s/t
  8. Repeat and calculate a mean
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9
Q

Ultrasound waves

A
  • Have a higher frequency than the limit of human hearing
  • ultrasound waves are partially reflected when they meet a boundary
  • the time taken for the reflections to reach a detector can be used to determine how far away such a boundary is
    -> this allows them to be used for medical and industrial imaging
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10
Q

Seismic waves

A
  • produced by earthquakes
  • p-waves: longitudinal seismic waves that travel at different speeds through solids and liquids
  • s-waves: transverse seismic waves that cannot travel through liquid
  • p-waves and s-waves produce evidence for the structure and size of the earths core
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11
Q

Electromagnetic waves

A

Transverse waves that transfer energy from the source of the waves to an absorber

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12
Q

Order or EM waves from longest wavelength to highest shortest wavelength

A
  • radio
  • microwaves
  • infrared
  • visible light
  • ultraviolet
  • xrays
  • gamma rays
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13
Q

Uses of the EM waves

A

Radio waves - television and radio

Microwaves - satellite communications and food

Infrared - electrical heaters, cooking food and infrared cameras

Visible light - fibre optic communications

Ultraviolet - sun tanning

X-rays and game rays - medical imaging and treatments

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14
Q

For a distant object that is placed more than twice the focal length from the lens, the image is…

A

inverted
diminished
real

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15
Q

For an object placed between one and two focal lengths from the lens, the image is:

A

inverted
magnified
real

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16
Q

When the object is placed at a distance less than the focal length. The image is:

A

upright
magnified
virtual

17
Q

Concave lenses always produce images that are:

A

upright
diminished
virtual

18
Q

Order the colour spectrum in increasing frequency and decreasing wavelength

A

red
orange
yellow
green
blue
indigo
violet

19
Q

What can happen to light waves between the boundary of 2 objects

A
  • Waves can be absorbed at the boundary between two different materials. When waves are absorbed by a surface, the energy of the wave is transferred to the particles in the surface. This will usually increase the internal energy of the particles.
  • Waves can also be transmitted at the boundary between two different materials. When waves are transmitted, the wave continues through the material. These materials are transparent because light is transmitted with very little absorption. Translucent materials transmit some light but are not completely clear.
20
Q

How do objects appear in white light

A

When white light shines on an opaque object, some wavelengths or colours of light are absorbed. These wavelengths are not detected by our eyes. The other wavelengths are reflected, and these are detected by our eyes.

21
Q

How do objects appear in coloured light

A

An object appears to be black if it absorbs all the wavelengths of visible light. For example, an object that appears blue in white light will appear black in red light. This is because the red light contains no blue light for the object to reflect.

22
Q

What is intensity

A

How much energy is transferred to a given area in a certain amount of time

23
Q

What is distribution of wavelengths

A

The spread of intensities of different wavelengths

24
Q

Objects temperature link to intensity and distribution

A

As temp increases the intensity of every emitted wavelength increases

As the temperature of an object increases the peak wavelength decreases

25
Q

Explanation of temp and intensity

A

A hotter object gives out more energy of every wavelength of radiation than a cooler object

26
Q

Explanation of temp and distribution

A

As an object gets hotter, the intensity increases more rapidly for shorter wavelengths -> a bigger amount of the radiation emitted by a hot object has a short wavelength compared to that emitted by a cooler object

27
Q

What are sound waves

A

Longitudinal waves of vibrating particles caused by vibrating objects -> these vibrations are passed through the surrounding matter as a series of compressions and rarefractions

28
Q

What happens when a sound wave enters a denser medium

A

It speeds up so it’s wavelengths increase

29
Q

How do microphones work

A

Sound waves cause a diaphragm to vibrate and this movement is converted into an electrical signal

30
Q

Human hearing range

A

20Hz - 20kHz

31
Q

How ears work

A

Sound waves of certain frequencies reach your ear drum and make it vibrate
-> these vibrations are passed on to ossicles in the ear through canals and to the cochlea
-> the cochlea turns these vibrations into electrical signals which get sent to your brain and allow you to hear the sound

32
Q

Properties of ultrasound

A

When waves pass from one medium into another some of the waves are reflected by the boundary between the 2 media and some of transmitted

-> this is partial reflection

33
Q

What does partial reflection in an ultrasound mean

A

You can point a pulse of ultrasound at an object

34
Q

How to measure how far away a boundary is

A

The time it takes for the reflections to reach a detector

35
Q

Ultrasound in medical imaging

A

Ultrasound waves can pass through the body but whenever they reach a boundary between 2 different mediums (like fluid in the womb and the skin of the foetus) some of the wave is reflected back and detected

36
Q

Echo sounding

A

Type of sonar used by boats where high frequency sound waves are used to find out the depth of the water or locate objects

-> sound waves are emitted by the boat and then the time taken for the echo to return is measured and then can be used to calculate distance to the object that reflected the sound (if u know the speed of sound in the water)

37
Q

What are ‘body waves’

A

Waves that travel through the earth, not across its surface

38
Q

What do seismic waves show

A
  • seismic waves’ paths curve showing that there is a gradual change in the density of the mantle
  • s waves aren’t detected on the opposite side of the earth showing that the outer core must be liquid
  • the existence of shadow zones where no P-waves are detected suggested the existence of a solid inner core
  • kinks in the paths of P-waves travelling to the other side of the earth suggest a sudden change in the density of the material they are passing through

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