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Physics 2 And 3 > P3 > Flashcards

P3 Flashcards

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1
Q

What are X rays like

A

They are part of the electromagnetic spectrum
They have a high frequency and a very short wavelength
They have high energy and can cause ionisation

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2
Q

What are the uses of X rays

A

Can form an image on an X Ray plate or with a CCD (electronic image)
Can take shadow pictures of bones to detect breaks and fractures
Can scan to detect problems with soft tissue e.g. Disease
Used for killing cancer cells in radiotherapy

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3
Q

What are the precautions

A

Only use if necessary and use as low a power as possible
Use a focuses beam during treatments so as not to expose areas of the body not being treated or examined
Technicians should take the X rays from behind a screen or wear lead clothing
Technicians should wear detection badges, which measure their exposure over time

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4
Q

What is ultrasound

A

Sound waves of frequencies greater than 20 000Hz

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5
Q

What happens when and ultrasonic waves pass from one medium into another

A

They are partly reflected at the boundary. The reflected waves are usually processed to produce a visual image on a screen

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6
Q

How do you measure how far away the boundary is

A

The time taken for the ultrasonic waves to be reflected

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7
Q

What is the use of ultrasounds in medicine

A

The mains use is in prenatal scans but it can also be used for other scans e.f. Detection of gesticulating cancer

It can also be used to break up kidney stones which can then be passed out of the body in urine. This saves having to operate on their patients kidneys

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8
Q

How does an ultrasound on a baby work

A

An ultrasound pulse is sent into the body and gets reflected back at different changes of density. These reflected waves are detected and used to form a picture of the foetus. Because ultrasound is non ionising it is safer to use use than X rays

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9
Q

How do you locate a flaw or crack in a block of metal

A

Some ultrasound waves are reflected back by the flaw or crack within the structure. The time taken for the reflected wave to return is used to calculate the location of the crack

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10
Q

Best to worse image quality of scanning methods

A

CT scans
X rays
Ultrasound

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11
Q

Most to least radiation exposure

A

CT scans
X rays
Ultrasounds

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12
Q

What is refraction

What does it depend on

A

The change of direction of light as it passes from one medium to another

The refractive index of the material and the angle of incidence

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13
Q

What is a lens

What are the two types of lens

A

A piece of transparent material that refracts light rays

Diverging
Converging

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14
Q

What is the focal length

A

The distance from the lens to the principal focus

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15
Q

What is a diverging (concave) lens like

A

Thin at the centre
The rays of light are refracted outwards so that they appear to have came from one point, the focus
The image produced by a diverging lens is virtual and upright

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16
Q

What is a converging (convex) lens like

A

Thick at the centre

The light rays are refracted inwards to converge at one point called the focus

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17
Q

What does the image produced by a converging lens depend on

A

The distance of the object from the lens

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18
Q

What is the image like if the distance from the object to the lens is longer than the distance from the lens to the focal point in a converging lens

When is this type of lens used

A

Real image
Inverted

In cameras

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19
Q

What is the image like if the distance from the object to then lens is less than the distance from the lens to the focus point in a converging lens

When is this type of lens used

A

Virtual image
Upright
Enlarged
Seems to be formed on the same side of the lens

In magnifying glasses

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20
Q

What does the adjustable convex lens do

A

Focuses on the image

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21
Q

Why does someone need glasses

A

Their lenses are unable to focus the image correctly on the retina

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22
Q

What does the retina do

What do lenses do

What does the cornea do

What does the pupil do

Why does the iris do

A

Focuses images

Focuses the images

Protects the eye and begins to focus the light

Light enters the eye here

Adjusts to alter the amount of light entering the eye

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23
Q

What do suspensory ligaments do

What do ciliary muscles do

A

Connect the lens to the ciliary muscles

Contract and relax to alter the shape of the lens so the eye can focus on objects at different distances

24
Q

In a camera:
What allows light to enter

What focuses the light

Adjusts focus for different distances

Controls amount of light entering

Forms the image

A

Aperture

Convex lens

Lens moves closer or further away from the film

Diaphragm/ aperture stop changes the aperture size

Photographic film or CCD chip

25
Q

What so the range of vision in a normal eye

A

Between the near point ( around 25cm) and the far point (infinity)

26
Q

What is the eye like if it’s short sighted

How do you correct short sightedness

A

The eyeball is too long or the lens is too fat. This means that near object are in focus, but distant objects are focused in front of the retina

Diverging lens

27
Q

What is the eye like if it’s long sighted

How do you correct long sightedness

A

The eyeball is too short or the lens is too thin. This means that distant objects are in focus, but near objects are focuses behind the retina

28
Q

What does the focal length and power depend on

A

The curvature- a more curved lens has a higher power and shorter focal length

The refractive index- a high refractive index has a higher power and shorter focal length

29
Q

What is internal reflection

A

When a ray of light travels from glass into air, some light is reflected at the interface

30
Q

When does total internal reflection occur

A

When the angle of incidence exceeds a certain value, called the critical angle

31
Q

When is a total internal reflection used in medicine

A

With endoscopes for internal examinations, which removes the need for surgery to see inside the patients body. The optical fibre is used to provide illumination inside the body by shining a light through the fibre

32
Q

What are the uses of lasers in medicine

Examples of surgical procedures using lasers

A

Cutting
Burning
Cauterising

Removing verrucas
Delicate laser eye surgery

33
Q

What is the momentum

A

The turning effect of a force

34
Q

How do you increase the moment

A

Increase the force applied

Increase the perpendicular distance between the line of action of the force and the pivot

35
Q

What is the centre of mass of an object

A

The point through which the whole worthy of the object is considered to act

36
Q

How do you find the centre of mass

A

Hang the sheet and a plumb line from one point so both are free to rotate. Mark the position of the plumb line as a vertical line
Hangs the sheet from a different position. Mark the position of the second plumb line
The centre of mass is the point where the two lines cross.

37
Q

Why would a car topple over

A

If the line of action of the weight of the car lies outside its base, the car will topple over

38
Q

How can the stability of car be increased

A

Lower centre of mass

A wider base

39
Q

Why can’t liquids be compressed

A

The particles are close together

40
Q

What happens when an object moves in a circle continuously

A

It accelerates towards the centre of the circle. This acceleration does not change the speed of the object, but the direction of its motion I.e. It’s velocity

The resultant force causing this acceleration is called the centripetal force

41
Q

What 3 things can increase the centripetal force

A

The mass of the object increasing
The speed of the object increasing
The radius of the circle decreases

42
Q

How is the size of the current increased (2)

A

Increases the size of the current

Increase the strength of the magnetic field

43
Q

How is the direction of the force reversed (2)

A

Reverse the direction of flow of the current

Reverse the direction of the magnetic field

44
Q

When is Flemings right hand rule used

A

To work out what direction the force induced will act

45
Q

What does each finger and thumb show in Flemings left hand rule

A

The first finger points in the direction of the magnetic field
The second finger points in the direction of the current flow
The thumb will then be pointing in the direction of the force

46
Q

What do transformers rely on to convert one voltage to another

A

Electromagnetic induction

47
Q

How is a potential difference induced

How will a current be induced

A

If a wire or a coil of wire cuts through the lines of force of a magnetic field

If the wire is part of a complete circuit

48
Q

How do you induce a current in one direction

A

Move the magnet into the coil

49
Q

How can a current be induced in the opposite direction

A

By moving the magnet out of the coil

By moving the other pole of the magnet into the coil

50
Q

Hal is the size of the induced potential difference increased

A

Increase the speed of movement of the magnet or the coil
Increase the strength of the magnetic field
Increase the number of turns on the coil

51
Q

What does a transformer do

What do transformers consist of

A

Changes the electrical energy from one potential difference to another potential difference

Two coils called the primary and the secondary coils, wrapped around a soft iron core

52
Q

How does the potential difference get from the primary coil to the secondary coil

A

An alternating potential difference across the primary coil will cause an alternating current to flow. This alternating current creates a continually changing magnetic field in the iron core, which induces an alternating potential difference across the secondary coil

53
Q

What is a step up transformer like

A

There are more turns on the secondary coil than the primary coil so the potential difference is greater leaving the secondary coil than that of the primary coil

54
Q

What is a step down transformer like

A

There are fewer turns on the secondary coil than the primary coil so the potential difference is lower leaving the secondary coil than that of the primary coil

55
Q

What happens when the voltage increases

A

The current decreases

56
Q

What are switch mode transformers

A

They are lighter and smaller than traditional transformers. They produce less heat and use very little power when no kid is applied. This makes them ideal for applications like mobile phone rechargers because their small size makes them more portable and once the phone is fully charged the transformer acts as a switch and so does not waste energy

Physics 2 And 3 (4 decks)

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