Physics Unit 3

?
  • Created by: Emily
  • Created on: 18-05-13 20:58
What are x-rays?
High frequency, short wavelanght electromagnetic waves
1 of 37
How are CT scans differnt to x-rays?
CT scans can produce high resolution images of soft and hard tissue, they can form 2D images throught the body which can be put together to form a 3D image
2 of 37
X-rays cause ionisation, what is this?
It is where high doses of the rays kill living cells, this can lead to damage, however if carefully focused and at the right dosage they can kill cancer cells
3 of 37
How are radiographers protected from exposure to x-rays?
They waer lead aprons, and stand behind lead screens which absorb the rays before they reach the body, otherwise they leave the room so they're not exposed
4 of 37
True or false, ultrasound is sound with a lower frequency than we hear
False, ultrasound is sound with a HIGHER frequency than we hear
5 of 37
What happens when ultrasound waves pass from one median to another?
Some of the wave if reflected off the boundary between the two media and some is transmitted (partial reflection)
6 of 37
Give one method that can be used to find the different boundaries
Using the traces of an oscilloscope
7 of 37
Identify 2 different uses of ultrasounds and briefly explain them
Breaking down kidney stones, high energy beams are concentrated at the kidney stone breaking it down into sand-like particles / Pre-natal scanning of a fetus, where waves are reflected back and detected when they reach a boundary forming an image
8 of 37
What is best, ultrasound, x-rays or CT scans? Give advantages and disadvantages of each
Ultrasound, very safe / images are fuzzy / harder to diagnose problems. X-rays, ionising so damaging / clear images of bones and metal. CT scans, very ionising / rarely taken / produce detailed images / diagnose complicated illnessed
9 of 37
Explain refraction
Refraction is when waves change direction as they enter a differnet medium
10 of 37
What happens if a wave hits a boundary at 90 degrees?
It will not change dirction
11 of 37
What is the refractive index and how do you calculate it?
Refrective index of a medium is the ratio of speed of light ina vaccum to speed of light in that medium, refractive index = sin(i) / sin(r)
12 of 37
What are the 2 types of lenses?
Convex lenses and concave lenses
13 of 37
What is the difference between the positions of the principal focus in convex and cancave lenses?
Convex: principal focus where rays hitting the lense parallel to the axis meet / Concave: principal focus point where rays hitting the lens parallel to the axis appear to come from
14 of 37
What type of lense does a magnifying glass use and what type of image does it produce?
It uses a converging lense (convex) and produces a magnified virtual image
15 of 37
Is the formula for power of a lense P = 1 / f ?
Yes
16 of 37
How can you work out the magnification of an image?
Magnification = image height / object height
17 of 37
Label 4 differnt parts of the eye
Cornea / iris / pupil / lens / ciliary muscle / retina / suspensory ligaments
18 of 37
The pupil is the hole in the middle of the eye that controls the intensity of light entering the eye, true or false?
True
19 of 37
What is the functuion of the lens in the eye?
It focuses light from objects at varying distances
20 of 37
What part of the eye is covered in light-sensitive cells where images form?
The retina
21 of 37
What is the far point of the eye?
The furthest distance that the eye can focus comfortably
22 of 37
Is the images formed on the retina the right way up or inverted?
Its inverted and then flipped the right way up
23 of 37
What type of lenses correct short sight?
Diverging lenses
24 of 37
How do converging lenses correct long sight?
They enable the the light to be refracted and start converging before it enters the eye so as to ensure that the image can be focused on the retina
25 of 37
What is total internal reflection?
When waves traveling from a dense to a less dense substance have an angle of incidence that is larger than its critical angle, meaning that the light cannot leave the more dense substance and is reflected internally within the substance
26 of 37
Give two advantages of using endoscopes
Allow doctors to see the inside of the body in a lot of detal / they mean operations can be performed without cutting patients open
27 of 37
How can the moment needed to turn a pivot be reduced?
By increasing the perpendicular distance from the moment to where the force is being applied, or by increaseing the force applied
28 of 37
What type of object would be more stable? Low and wide or tall and thin?
Low and wide because they would have a lower centre of mass
29 of 37
True or false, pressure uin a liquid is transitted equally in all directions?
True
30 of 37
If an object is travelling in a circle, what happens to its velocity?
It's constantly changing, due to a chance in direction and not speed
31 of 37
Where is acceleration acting towards in an object in circular motion?
Towards the centre of the circle
32 of 37
What is the force that keeps someting moving in a circle called?
The centripetal force
33 of 37
What do magnetic materials and wires carring currents experience in a magnetic field?
A force acting upon them
34 of 37
What 2 factors can be used to speed up a simple electric motor?
Adding more current / a stronger magnetic field
35 of 37
The creation of a potential differnce across a conductor which is experiencing a change in magnetic field, is the definition of what?
Electromagnetic induction
36 of 37
What is the main difference between a step-up transformer and a step-down trasformer?
A step-up transformer have more turns on the the secondary coil, whereas a step-down transformer has more turns on the primary coil
37 of 37

Other cards in this set

Card 2

Front

How are CT scans differnt to x-rays?

Back

CT scans can produce high resolution images of soft and hard tissue, they can form 2D images throught the body which can be put together to form a 3D image

Card 3

Front

X-rays cause ionisation, what is this?

Back

Preview of the front of card 3

Card 4

Front

How are radiographers protected from exposure to x-rays?

Back

Preview of the front of card 4

Card 5

Front

True or false, ultrasound is sound with a lower frequency than we hear

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Physics resources:

See all Physics resources »