BMSAT > Waves > Flashcards

Waves Flashcards

(58 cards)

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1
Q

What do waves transfer?

A

Energy

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2
Q

What is frequency?

A

Number of complete waves passing a certain point each second

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3
Q

What is a period?

A

Amount of time it takes for a complete wave to pass a point

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4
Q

What is amplitude?

A

Height of a wave from the midpoint

(Maximum displacement of a point on a wave from its rest position)

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5
Q

What is the wavelength?

A

The length of a full cycle of the wave (from peak to peak/two same points)

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6
Q

What can happen to a wave that hits a boundary?

A

It can be absorbed, transmitted or reflected

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7
Q

What are transverse waves and give an example?

A

Oscillations perpendicular to the direction of the energy transfer

Ripples in water, EM waves

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8
Q

What are longitudinal waves and give an example?

A

Oscillations are parallel to the direction of energy transfer

Sound waves, P-waves

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9
Q

What are the two parts of a longitudinal wave called?

A

Rarefactions and compressions

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10
Q

What is wave speed?

A

The speed at which a wave transfers energy

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11
Q

What is one Hz equal to?

A

1 wave per second

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12
Q

How to measure the speed of sound?

A
  1. Speaker is attached to a signal generator of a specific frequency
  2. Microphones are connected ti an oscilloscope
  3. Waves detected at each microphone are shown as separate waves
  4. One microphone moved until the waves line up (peaks and crests match)
  5. Distance between the microphones is equal to one wavelength
  6. Use wave equation to find speed.
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13
Q

In reflection, what is the relationship between angle of reflection and incidence?

A

They are always equal to one another

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14
Q

What is diffuse reflection?

A

Rays are reflected off of a rough surface and are scattered - surface then appears matte

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15
Q

What is specular reflection?

A

Rays are reflected off of a smooth surface and all reflected rays travel in one direction - surfaces gives a clear reflection

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16
Q

What is refraction?

A

When a wave changes direction when it crosses a boundary between two mediums at an angle to the normal

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17
Q

What happens when a refracted wave slows down?

A

Wavelength decreases and bends towards the normal

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18
Q

What happens when a refracted wave speeds up?

A

The wavelength increases and bends away from normal

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19
Q

What is the order of EM spectrum from the lowest frequency?

A

Radio waves
Microwaves
Infrared
Visible light
Ultraviolet
X- rays
gamma rays

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20
Q

What are the characteristics of EM waves?

A
  • They are transverse waves
  • They transfer energy from source to absorber
  • They travel at the same speed in air or in a vacuum
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21
Q

How are radio waves produced?

A

Produced by oscillations in electrical circuits

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22
Q

How are radio waves transferred?

A
  1. Emitted radio waves transfer energy from transmitter
  2. A receiver absorbs the radio waves causing the electrons to oscillate
  3. Ac is induced in the receiver at the same frequency
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23
Q

What are radio waves used for?

A

TV
Radio

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24
Q

What are microwaves used for?

Study These Flashcards
A

Satellite communication
Cooking

25
What is infrared radiation used for?
Electric heaters Cooking Infrared cameras
26
What is visible light used for?
Communications through optical fibres
27
What is UV used for?
Energy efficient lights Sun tan beds
28
What are x-rays and gamma rays used for?
Medical imaging Medical treatments
29
What is the radiation dose and what is it measured in?
The measure of the risk of harm to body tissues due to exposure to radiation Measure in sieverts
30
What does risk of radiation dose depend on?
Size of dose and type of radiation
31
How can UV harm the body?
Can prematurely age skin Increases risk of skin cancer
32
How can x-rays and gamma rays cause harm?
Gene mutations and cancer
33
What is a real image?
Image formed when light rays from a point on an object come together at another point
34
What is a virtual image?
Image formed when light rays appear to have come from one point but in reality they come from another
35
How do lenses form images?
By refracting light
36
What is the difference between the images a convex and concave lens can produce?
A convex lense can produce real or virtual images A concave lens can only produce virtual images
37
What is the focal length?
Thr distance between the centre of the lens and the principal focus
38
What is the principal focus in a convex and concave lens?
In a convex lens its the point at which all rays come together that have hit the the lens parallel to the axis In a convex lens its the point at which all rays appear to come from
39
What do magnifying glasses do?
Use convex lenses to create a virtual image - object is magnified Larger image height = larger magnification
40
What are the characteristics of an opaque object?
Does not transmit light Colour depends of wave length of light that is most reflected
41
What are the characteristics of transparent or translucent objects?
They transmit light Colour depends on wavelength of light that it transmits or reflects
42
What do colour filters do?
They transmit certain colours (wavelengths) and absorb the rest of the
43
What happens if all wavelengths are absorbed or reflected?
All wavelengths absorbed = black All wavelengths reflected = white
44
What happens when an object and its surroundings are the same temperature?
The object is emitting and absorbing Infrared radiation at the same rate It keeps its constant temperature
45
What happens when an object is colder than its surroundings?
The object absorbs IR radiation faster than it emits it Which increases its temperature
46
What is a perfect black body?
An object that absorbs all radiation that hits it
47
What are the properties of a perfect black body?
Best possible emitters of radiation Don’t reflect or transmit any radiation
48
What happens to intensity and wavelength of emitted radiation as temperature increases?
The intensity of every wavelength increases and peak wavelength decreases
49
What is happening during daytime on earth?
The earth is absorbing more radiation than it emits so temperature increases
50
What is happening at nighttime on earth?
The earth emits more radiation than it absorbs so temperature decreases
51
What happens when a sound wave enters a denser material?
- wavelength increases - frequency stays the same - wave speed increases
52
How can we hear sound?
Sound waves hit ear and cause ear drum to vibrate The vibrations cause other parts of the ear to vibrate allowing you to hear sound waves
53
What is the normal human hearing age?
20Hz -20kHz
54
What are three factors that can limit frequency range that can be heard?
Size of ear drum Shape of ear drum Structure of all parts within the ear that vibrate
55
What is ultrasound?
Sound waves with frequencies higher than 20 kHz
56
What are three uses of ultrasound?
1. Medical imaging 2. Industrial imaging e.g finding flaws in materials 3. Echo sounding
57
What are p-waves and what do they travel through ?
Longitudinal waves that travel through solids and liquids -pass through core Faster through solids
58
What are s- waves and what do they travel through?
Transverse waves that cant travel through liquids - don’t pass through core
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