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p1 Flashcards

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1
Q

wave speed (m/s)

A

= frequency(Hz) x wavelength(m)

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2
Q

Transverse waves have

A

perpendicular disturbances

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3
Q

Longitudinal Waves have

A

parallel disturbances

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4
Q

How do you measure the speed of sound?

A

Using an oscilloscope

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5
Q

Measure frequency using a ripple tank by:

A

Float a cork in the ripple tank, begin the waves and start the stop watch; time how long it takes for 10 bobs to occur. Divide the time taken by 10 to find the time for one bob.

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6
Q

Measure the wavelength using a strobe light by:

A

placing a card covered with centimetre squared paper behind the ripple tank. Turn on the strobe and adjust its frequency until the waves appear to “freeze”. Using the squared paper, measure the distance that say 5 waves cover. Divide that number by 5 to calculate an average wavelength.

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7
Q

Measure the wavespeed using a pencil and a stopwatch by:

A

Place a large piece of paper next to the tank. As the waves move across the tank, one person should track the path of one of the crests on the paper using a pencil. Another person should time how long it takes the first to draw a line of a certain length. Then calculate wave speed by plugging the length of the line into the equation speed= distance/time.

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8
Q

When a wave meets a boundary between two materials, the wave can be:

A

ABSORBED by the second material- its energy is transferred to the material, often causing heating.

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9
Q

When a wave meets a boundary between two materials, the wave can be:

A

TRANSMITTED through the second material- the wave carries on travelling through the new material. This often leads to refraction.

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10
Q

When a wave meets a boundary between two materials, the wave can be:

A

REFLECTED- this is where the incoming ray is neither absorbed nor transmitted, but instead is “sent back” away from the second material.

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11
Q

If wave speed increases…

A

the wavelength also increases.

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12
Q

If wave speed decreases…

A

the wavelength also decreases

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13
Q

When a wave crosses a boundary between materials…

A

…it changes speed.

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14
Q

If a wave hits the boundary at an angle to the normal…

A

…this causes a change in direction but also a change in speed; and is known as refraction.

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15
Q

The greater the change in speed…

A

…the more a wave bends (changes direction).

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16
Q

If the wave speeds up…

A

…the wave will bend away from the normal.

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17
Q

If the wave slows down…

A

…the wave will bend towards the normal.

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18
Q

The Electromagnetic spectrum are

A

transverse waves and they all travel at the same speed.

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19
Q

Order of the electromagnetic is:

A 
Radio waves
micro waves
infrared waves
visible light
ultra violet 
x-rays 
gamma rays
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20
Q

White light is actually…

A

…a mixture of all the colours across the visible spectrum.

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21
Q

What radiations are emitted when their electrons drop down energy levels?

A

Visible light, UV, X-rays.

22
Q

What happens when EM waves are absorbed?

A

When any type of EM is absorbed, it ceases to exist as radiation and causes heating. However very high energy UV, Xrays and gamma rays have so much energy that they don’t only cause heat, but they can also cause ionisation when absorbed by molecules.

23
Q

If an atom is ionised it has…

A

lost an electron- if an outer electron absorbs radiation with enough energy, it can move so far that it leaves the atom, It is now a free electron and the atom is said to of been ionised.

24
Q

Ionising radiation are harmful because?

A

Gamma radiation, high energy UV and X-rays are types of ionising radiation- they all carry enough energy to kt amounts of exposure to ionising radiation can be dangerous as the radiation can react causing cell damage and even cell destruction. The change in the cell could cause them to grow in an uncontrollable and possibly lead to cancer.

25
Q

Ultraviolet radiation is absorbed…

A

…by the skin, where it can cause damage to cells, possibly leading to cancer.

26
Q

X-rays and Gamma radiation can cause…

A

…mutations and damage cells too. They are very dangerous because they carry a lot of energy and are very penetrating and pass through the skin and are absorbed by deeper tissues.

27
Q

What are radio waves used for?

A

We use radio waves to transmit information like television and radio shows from one place to another.

28
Q

What are microwaves used for?

A

They are used both for communications and cooking. Communication to and from satellites uses microwaves with a wavelength that can only pass easily through the Earth’s watery atmosphere.

We also use microwaves of a slightly different wavelength to cook food. The microwaves penetrate up to a few centimetres into the food before being absorbed and transferring energy to water to heat up. The water molecules then transfer energy to the rest of the molecules in the food which quickly cooks the food.

29
Q

What is infrared radiation used for?

A

Infrared radiation is given off by all objects. The hotter the object the more that is given off. Infrared cameras can detect IR radiation and monitor temperature. They display it on a screen as a picture, and the hotter an object is the brighter it is displayed.

30
Q

What is ultraviolet radiation used for?

A

Ultraviolet is used in fluorescent lamps. Fluorescent lights use UV radiation to emit visible light. They’re energy efficient so they’re good to use when light is needed for long period of times.

31
Q

What are X-rays used for?

A

X-rays can be used to view the internal structure of objects and materials, including human bodies. Radiographers in hospitals take X-ray images to help doctors identify a broken bone. They are transmitted by flesh but absorbed by denser materials such as bone.

32
Q

What are Gamma rays used for?

A

Gamma rays are used to sterilise things such as medical equipment. They are good because they can kill any microbes (bacteria) that are hidden, because they can travel straight through the medical instruments.

Food can also be sterilised in the same way (by killing microbes) which keeps the food fresher for longer.

33
Q

How does radiation affect the worlds temperature?

A

The overall temperature of the Earth depends on the amount of radiation it reflects, absorbs and emits. During the day lots of EM radiation is emitted by the Sun to the Earth. The atmosphere allows some of it to pass through to be absorbed by the Earth which increases local temperatures. However at night less EM radiation is emitted so it is colder. Overall the temperature has a fairly constant temperature and pattern.

34
Q

What are the main greenhouse gasses?

A

Carbon dioxide, methane and water vapour.

35
Q

What do the greenhouse gasses do to the Earth and the atmosphere?

A

The 3 main greenhouse gasses trap radiation in the Earth’s atmosphere- this is a contributing factor to why the Earth is warm enough to support life. Greenhouse gasses absorb lower frequency radiation, so they absorb a large amount of the radiation emitted by the Earth. The greenhouse gasses then re-emit the radiation in all directions- including back towards Earth.

36
Q

Forms of human activity that affect the amount of greenhouse gasses in the atmosphere:

A

Deforestation: This is where humans cut down and burn forests to clear land. Fewer trees mean less CO2 is removed from the atmosphere.
Burning fossil fuels: Carbon that was “locked up” in these fossil fuels are released as carbon dioxide when burnt.
Creating waste: More landfill sites and more waste from agriculture means more CO2 and methane released as waste decays.

37
Q

How is carbon dioxide linked to climate change?

A

Over the past 200 years the percentage of carbon dioxide in the atmosphere has increased. This is mainly due to an increase in burning of fossil fuels. Recently the average temperature of the Earth has been increasing. Most scientists agree that the extra carbon dioxide from human activity is causing this increase.

38
Q

What is a concave lens?

A

A concave lens is a a lens that caves inwards. It causes parallel rays of light to diverge (spread out).

39
Q

What is a convex lens?

A

A convex lens (converging) bulges outwards. It causes parallel rays of light to converge (be brought together)

40
Q

Sounds travels as a:

A

wave.

41
Q

Sounds waves are caused by:

A

vibrating objects.

42
Q

Which is faster; the speed of sound or the speed of light?

A

The speed of light.

43
Q

What is Ultrasound?

A

Ultrasound is sound with frequencies higher than 20,000 Hz.

44
Q

How can ultrasound be useful?

A
  • Ultrasound can be useful because ultrasound waves can pass through the body, but whenever they reach a boundary between two different media, some of the wave is reflected back and detected.
  • Ultrasound can also be used to find flaws in objects such as pipes or materials such as wood or metal. If there is a flaw such as a crack inside the object the wave will be reflected sooner.
45
Q

When a wave hits a boundary between materials what can happen?

A

The wave might be completely or partially reflected; like in ultrasound waves. The wave might continue travelling in the same direction but at a different speed. Or it might be refracted or absorbed.

46
Q

What can cause seismic waves?

A

Both Earthquakes and Explosions cause seismic wave.

47
Q

What is a seismic wave?

A

Seismic waves are waves of energy that travel through the Earth’s layers, and are a result of earthquakes, volcanic eruptions, magma movement, large landslides and large man-made explosions that give out low-frequency acoustic energy.

48
Q

What are the 3 types of seismic waves?

A

The 3 types of seismic waves are:

  • L waves
  • S waves
  • P waves
49
Q

P waves:

A
  • P waves travel along the surface of the Earth.
  • P waves are longitudinal
  • P waves travel through solids and liquids.
  • They travel faster then S waves
50
Q

S waves:

A

-S waves travel along the surface of the Earth.
-S waves are transverse and can only travel through solids.
They are slower than P waves.

Physics (6 decks)

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