Physics - Tripple

Question 0

How are images formed by using X rays?

Answer 0

Images can be formed electronically by using a charge - coupled device (CCD)
Silicon chips are divided up into grids of millions of identical pixels these detect X rays and produce electronic signals which are used to form high resolution images

Question 1

What can a X ray be absorbed by?

Answer 1

Bone and metal

They pass through healthy tissue

Question 2

How does a CT scanner work?

Answer 2

1. Patient is put inside a cylindrical scanner
2. X rat beam fired through the body from an Xray tube and picked up by detectors on opposite side
3. X ray tube and detectors are rotated in the scan
4. Computer intercepts signal and forms a 2D images
5. Lots of scans can be put together to form a 3D image

Question 3

How are X rays used to treat cancer?

Answer 3

1. X ray is focused on tumour using a wide beam
2. Beam is rotated round the patient with the tumour at the centre
3. This minimises the exposure of normal cells to radiation and reduces the risk of damaging the body

Question 4

How do you minimise the radiation dosage?

Answer 4

Lead apron
Lead screen
Leave room
Lead is issued to shield other parts of body 
Film badge

Question 5

How does ultrasound work?

Answer 5

When a wave passes from one medium to another some is reflected, the ultrasound measure the time it takes for the reflections to reach a detector and measures how far an object is away

Question 6

How do you measure the distance travelled by the pulse?

Answer 6

Speed of ultrasound waves x transit time

Question 7

How do you work out the depth of the boundary below the surface?

Answer 7

0.5 x speed of ultrasound waves x transit time

Question 8

How are ultrasounds used to break down kidney stones?

Answer 8

The ultrasounds concentrate high energy waves at the kidney stone turning it into sand like particles that pass out the body into the urine

Question 9

How do ultrasounds scan a pre-natal foetus?

Answer 9

The ultrasound pass through the body until it reaches the boundary between the womb fluids and the skin of the baby some of the wave is reflected back and detected on a computer, the exact timing and distribution of the echoes are processed into a computer producing an image

Question 10

What are the unsafe risks of waves? ( ultrasounds, x rays, CT scans?

Answer 10

Ultrasounds are non ionising so are safe
X rays are ionising
CT scans are even more ionising these will cause cells to mutate

Question 11

What are the images like of various waves?

Answer 11

Ultrasound - fuzzy
X rays - clear images of bone
CT scans - detailed images with high resolution

Question 12

What is total internal reflection?

Answer 12

When a substance travels through a dense substance towards a less dense substance

Question 13

If the angle of incidence is bigger than the critical angle ….

Answer 13

Most of the light passes out but a small amount is internally reflected

Question 14

If the angle of incidence is equal to the critical angle …

Answer 14

Goes along the surface but there is a lot of internal reflection

Question 15

If the angle of incidence is greater than the critical angle ….

Answer 15

All of it is internally reflected

Question 16

How does an endoscope work?

Answer 16

Consist of 2 bundles of optical fibres
One carries light towards and the other carries and image back
Image is seen through an eye piece or TV
Perform key hole surgery

Question 17

What is a converging lens?

Answer 17

Also known as a convex lens
Its a lens that makes light rays parallel to the principal axis to converse at the principal focus
The principal focus of a converging lens is where rays hitting the lens parallel to the axis all meet

Question 18

What is a diverging lens?

Answer 18

Also know as a concave lens
Its a lens that makes light rays parallel to the axis diverge as if from a single point
The principal focus of a diverging lens is the point where rays hitting the lens parallel to the axis appear to come from

Question 19

What is a principal focus?

Answer 19

The point where light rays parallel to the principal axis of a lens are focused or appear to diverge from

Question 20

What are the three rules of refraction in a converging lens?

Answer 20

1. An incident ray parallel to the axis refracts through the lens and passes through the principal focus on the other side
2. An incident ray passing through the principal focus refracts through the lens and travels parallel to the axis
3. An incident ray passing through the centre of the of the lens carries on in the same direction

Question 21

What affects the image?

Answer 21

Distance affects the image
The closer the object the bigger the image
If the image is closer than F it will make a virtual image the right way up and bigger than the object on the same side

Question 22

What are the three rules of refraction in a diverging lens?

Answer 22

1. An incident ray parallel to the axis refracts through the lens and travels in line with the principal focus
2. An incident ray passing through the lens towards the principal focus refracts through the lens and travels parallel to the axis
3. An incident ray passing through the centre of the lens carries on in the same direction

Question 23

What is a real image?

Answer 23

Light from an object comes together to form an image on screen

Question 24

What is a virtual image?

Answer 24

An image seen in a lens or mirror from which light rays appear to come from after being refracted by the lens or reflected by the mirror

Question 25

How do you describe an image?

Answer 25

How big it is in comparison to the object Upright or inverted Real or virtual

Question 26

What kind of image does a diverging lens produce?

Answer 26

A virtual image Right way up Smaller than object On same side of lens as the object

Question 27

What does an object have to be to be magnified?

Answer 27

Closer to the lens that the focal length Virtual image Cannot be projected on to a screen

Question 28

In what way is focal length related to power?

Answer 28

The more powerful the lens the more strongly it converges rays of light

Question 29

Is a converging lens negative or positive in power?

Answer 29

Positive | Diverging is negative

Question 30

What is focal length determined by?

Answer 30

Refractive index of lens material | Curvature of the 2 surfaces of the lens

Question 31

Name the components of the eye

Answer 31

``` Iris Cornea Pupil Ciliary muscle Eye muscle Lens Suspensory ligaments Retina Blind spot Optic nerve ```

Question 32

What does the retina do?

Answer 32

The retina is where images are formed covered in light sensitive cells which detect light and send signals to the brain to be interrupted

Question 33

What does the lens do?

Answer 33

The lens changes shape to focus light from varying distances. Its connected to the ciliary muscles and suspensory ligaments. When the ciliary muscles contract this builds up tension and makes the lens go flat and spherical. When the ciliary muscles relax tension the lens becomes thinner and flatter

Question 34

What does the ciliary muscle do?

Answer 34

Changes the thickens of the lens

Question 35

What does the iris do?

Answer 35

Its the coloured part of the eye that controls the light intensity and the size of the pupil

Question 36

What does the cornea do?

Answer 36

Its the transparent window and has a convex shape and a high refractive index this focuses the eye

Question 37

How does the eye focus on closer subjects?

Answer 37

As the eye focuses the power of the lens increases and the lens changes shape and the focal length decreases but the distance between the lens and object stay the same

Question 38

How does a camera work?

Answer 38

For a distance object the distance from the lens to the film must be equal to the focal length if the lens. The nearer and object is to the lens the greater the distance from the lens to the film

Question 39

What kinda image does a camera form?

Answer 39

Real inverted image thats smaller than the object due to the object being further away than the focal length same thing happens in our eye

Question 40

What is short sight cause by?

Answer 40

Its when the eye cannot focus on distance objects this is caused by the eyeball being too long or the cornea and lens being too powerful so the light rays form in front of the retina instead

Question 41

How do you fix short sight?

Answer 41

Short sight is corrected with a diverging lens, the diverging lens has negative power so reduces the power and diverges the light before it enters the eye focusing it

Question 42

What is long sight caused by?

Answer 42

Its when the eye cannot focus on near objects. | Caused by the eye being too short or the lens and cornea being too weak this mean images are formed behind the retina

Question 43

How is long sight corrected?

Answer 43

Corrected by putting a converging lens in front this has positive power which increases the amount of power in the eye. The converging lens refracts the light before it enters the eye focusing it on the retina.

Question 44

How does laser eye surgery work?

Answer 44

The laser vaporises the cornea to change the shape and therefore change the focusing of the retina. Laser eye surgery can increase or decrease power.