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School - Year 8 > Science - Physics 1 > Flashcards

Science - Physics 1 Flashcards

1
Q

How do we see things

A

We see things when light reflects off them and enters our eyes.

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2
Q

Where and how does light travel?

A

Light travels from a source in straight lines

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3
Q

What happens when light is shun on an opaque object?

A

Light cannot travel through opaque substances so it forms a shadow behind the substance.

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4
Q

What is light?

A

Light is a way of transferring energy from one place to another.

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5
Q

Properties of light

A

Transverse wave
300000000m/s in the air
travels through vacuum, gases, some liquids, some solids

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6
Q

Properties of sound

A

Longitudinal wave
330m/s in the air
travels through matter

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7
Q

How can we show how light travels?

A

By drawing rays.

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8
Q

What happens when light hits transparent materials?

A

Light can pass straight through transparent materials. We say light is transmitted through these materials.

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9
Q

What happens when light reaches opaque materials

A

Some of it is reflected and some is absorbed, when an object absorbs energy it warms up.

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10
Q

Camera obscura

A

A camera obscura is a room with a small hole in the wall. People inside the room can see an image of the outside world on the wall opposite the hole.

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11
Q

Pinhole camera

A

Pinhole camera is a small version of a camera obscura

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12
Q

How does a pinhole camera form an image on the screen

A

A pinhole camera forms an image on the screen because light from the object travels in straight lines.

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13
Q

Ray box

A

A ray boxes are the budgeted form for using lasers in school.

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14
Q

What is a plane mirror

A

A plane mirror is a flat mirror

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15
Q

Ray tracing

A

You can investigate what happens when a ray of light hits a mirror using a ray box. The method described is called ray tracing.

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16
Q

Incident ray

A

The light travelling towards the mirror is called the incident ray

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17
Q

Normal line

A

The normal is a line at right angles to the mirror. This is usually drawn as a dotted line. The angles of the light rays are measured from the normal.

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18
Q

Reflected ray

A

The light travelling away from the mirror is called the reflected ray.

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19
Q

what are mirrors made out of?

A

Mirrors are made of glass with a very thin layer of metal at the back. Mirrors reflect light evenly because the metal is very smooth.

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20
Q

Law of reflection

A

Angle of incidence = angle of reflection

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21
Q

Diffuse reflection

A

The light reflected by most opaque materials is scattered, so that it travels in all directions. This is called diffuse reflection.

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22
Q

Lense

A

Lenses are curved pieces of glass or other transparent material.

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23
Q

What are examples of lenses used in objects?

A

Microscopes, to make things look bigger
Telescope, to make distant objects look closer
Specs, to see more clearly
Spotlights, to focus beams of light
Cameras, to make sure the image is clear

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24
Q

What is refraction

A

The change of direction of light is called refraction. Refraction happens whenever light travels from one transparent substance to another. It only takes place where two substances meet (at their interface). If the light passes through the interface at 90 degrees, it does not change direction.

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25
Why does refraction happen?
Refraction happens because light travels at different speeds in different materials. It travels more slowly in substances such as water or glass than it does air
26
In which direction does light refract to when it travels through denser materials?
It travels toward the normal
27
In which direction does light refract to when it travels through less dense materials?
Away from the normal
28
Focal length
The focal length is the distance between the centre of the lense and the focal point
29
Focal point
The point where the rays meet is called the focal point.
30
What does the sensor do in the camera?
The sensor in the camera detects light falling on it because the energy transferred by the light causes electrical changes. The sensor changes energy transferred by light into electrical signals as well.
31
What do older cameras use to record images?
A film
32
What happens when light hits the film
Light hitting photographic film causes chemical changes that are then made permanent by developing the film with other substances
33
Lens in a camera
The lens focuses the light. The position of the lens can be adjusted so that the camera can focus on close or distant objects.
34
What does a shutter do in a camera?
The shutter stops light hitting the sensor when the camera is not in use. The shutter opens when a photo is being taken.
35
What is the aperture in a camera?
The aperture is a hole that can be adjusted to allow different amounts of light into the camera
36
What side facing is the image on the retina?
The retina is upsidedown, your brain makes you view it the right way up.
37
What is the iris?
The iris is the coloured part of the eye. It has a hole in the middle called the pupil. The iris can change the size of the pupil to control the amount of light entering the eye. This helps to prevent damage to the eye if the light is very bright.
38
What does the lens do in the eye?
The lens helps focus the light
39
Optic nerve
Nerve impulses are sent to the brain along the optic nerve
39
What is the cornea?
The transparent covering of the eye is called the cornea
39
What do the special cells in the retina do?
Special cells in the retina change the energy transferred by light into electrical impulses called nerve impulses
40
What cells does the centre of the retina contain?
Mainly cone cells, there are three types of cone cells which detect red, green and blue.
40
What cells do the outer parts of the retina contain?
Rod cells, which can detect quite low light levels but do not detect colours
41
What are the primary colours of light?
Red green blue are primary colours
42
What are the secondary colours of light?
Yellow, magenta, cyan are secondary colours
43
What is a tertiary colour?
All three primary colours mix to form white light
44
What do we think of daylight as?
whitelight
45
What is white light made from?
Different frequencies of light
46
How do rainbows form in the sky?
When white light from the sun is splut up by drops of rain in the air
47
How else can you split white light?
Using a prism
48
What are the colours of the rainbow called?
A spectrum
49
What happens when white enters a prism?
When white light passes through a prism the different frequencies are refracted by different amounts, so the colours spread out.
50
Which color is refracted the least and the most from white light?
Red is refracted the least, violet the most.
51
What is the seperation of colours called?
Dispersion
52
The colours in the spectrum are
Red orange, yellow, green, blue, indigo and violet
53
Why are objects around us percieved as different colours?
Objects around us appear to be different colours because they absorb and reflect different parts of the spectrum.
54
What colours do black objects absorb?
All of the colours
55
How do you make coloured light?
By using filters. As white light passes through a filter, some of the colours are absorbed. For example, a red filter only allows red light to pass through
56
what are particles always doing?
Moving
57
What is the energy stored in the movement of particles called?
Internal energy
58
What is another way of saying internal energy
Thermal energy
59
What is energy measured in?
Joules (J)
60
What is temperature?
Temperature describes how hot or cold an object is, it is measured using degrees celcius
61
How can we measure temperature?
Using a thermometer
62
What is the factors of how much internal energy is in an object?
Its temperature the material it is made from its mass
63
How can energy stored in a substance be transferred?
By heating
64
How does energy flow?
From hotter objects to cooler objects, the cool object becomes hotter and the hot object becomes cooler until they are both at the same temperature.
65
What changes the rate of energy being transferred through substances?
The bigger the temperature difference, the faster the energy is transferred.
66
What is another way of transferring energy?
Evaporation
67
When does a liquid evaporate fastest?
A liquid evaporates fastest on its boiling point, but it can evaporate at any temperature
68
What are the fastest-moving particles in a liquid
The fastest-moving particles in a liquid are the ones that escape to form a gas.
69
How can energy be transferred
Energy can be transferred by heating in several ways: evaporation, radiation, conduction and convection
70
What type of radiation is given off by hot objects
Infrared radiation
71
Do all things emit infrared radiation?
Yes, hotter the object, more radiation emits.
72
What happens when radiation hits something?
It can either be absorbed or reflected.
73
How does infrared radiation travel?
Through waves, in a similar way to light. It does not need a medium to travel through
74
What are thermal imagers
Thermal imagers are instruments that measure infrared radiation and convert the data into maps of temperatures. Thermal imaging can be used for filming things at night
75
What happens when a solid is heated?
The particles vibrate more, these vibrations pass through the solid
76
Are metals good thermal conductors?
Metals are good thermal conductors
77
What are good thermal insulators?
Wood and plastics
78
When does conduction best happen?
Solids, it doesn't go very well in liquid. and hardly happens in gases because the particles are far apart.
79
How is energy transferred through fluids?
Through convection
80
What happens when a part of a fluid is heated? Explain what convection current is as well
When part of a fluid is heated it expands and becomes less dense than the fluid around it. It floats upwards through the remaining fluid. Cooler fluid moves in to take its place and a convection current forms. Convection currents can also form when a part of a fluid is colder than its surroundings.
81
How can people keep their houses warm? give examples of good insulators
By burning fuel or heating, insulation can help to keep the warmth inside the house and save money on fuel bills. Brich, wood and other building materials are good insulators.
82
Air being conductor or an insulator
Air is an inferior conductor because the particles are far apart. Air does allow convection to take place, so air is a good thermal insulator only when it cannot move.
83
What colours reflect infrared radiation?
Light colours and shiny surfaces reflect infrared radiation, so painting houses white helps to keep them cool in summer. They are also poor emitters of infrared radiation.
84
What colours absorb infrared radiation?
Dark colours absorb and emit infrared radiation well, so solar panels (used to heat water) are painted black.
85
Why is a scientific investigation usually carried out?
A scientific investigation is usually carried out to test a hypothesis and reach a conclusion.
86
What is a valid conclusion?
A valid conclusion is one that relates to the original question being investigated and is only based on the evidence. A valid conclusion needs good-quality data that is accurate and precise.
87
What is accuracy
A measurement is accurate if it is close too the true value of the thing being measured. Measuring devices that have smaller divisions on their scales can measure more accurately than the ones with larger divisions, if they are set up correctly.
88
Why are accurate measures not always better?
Accurate measurements are not always better. They may be harder to make, take more time or use complicated apparatus. You must choose a level of accuracy bu thinking about the results you need in order to draw a conclusion, and how easy it will be to do the experiment. You may also have to justify a level of accuracy. This means you have to say why you use or do not use more accurate measurements.
89
What is precision
Measurements are precise if several measurements of the same thing give the same results. The closer together repeated measurements are, the more precise the data is (and the smaller its range). You cannot tell how precise your measurements are if you only take one reading - this is why scientists often repeat an experiment several times.
90
What are systematic errors
Systematic errors are that all the readings from these instruments are incorrect by a similar amount.
91
What is an example of a random error?
Results can also have random errors. For example, when measuring temperature, you might look at the thermometer scale from a slightly different angle each time you read it. Instruments with a digital readout avoid this problem.
92
What is power?
The amount of energy transferred per second is the power of an appliance.
93
What is the unit for power
Watt or Kilowatt
94
How can we find out the power of an appliance ?
We can find out how much energy different appliances transfer by looking for their power ratings.
95
The higher the power rating?
The more energy transferred per second
96
What is efficiency?
The amount of useful energy transferred compared with the total amount of supplied is the efficiency of an appliance.
97
What does wasted energy usually do?
Wasted energy usually makes the surroundings warmer.
98
What does a Sankey diagram show?
We can use a sankey diagram to show energy transfers. The width of each arrow represents the proportion of energy.
99
What is the efficiency formula?
Efficiency = (useful energy transferred / total energy transferred) * 100 %
100
What units do energy companies use?
kWh, killowatts per hour, how much energy has been spent in hours
101
formula for kWh
kWh = power rating (kW) * time (hours)
102
What is the formula for payback time, what is payback time?
Sometimes buying a new, more efficient appliance or improving the insulation can cost more money than it will save you. The payback time tells you how long it will take to save the money that an efficiency measure costs: paybacktime = cost of change / saving per year

School - Year 8 (11 decks)

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