Chapter 1

Question 0

Ultrasound

Answer 0

Short pulses of sounds are sent out from the scanner. They are reflected back when the density of the tissue changes

Question 1

Resolution

Answer 1

The smallest size of thing which can be distinguished. The better the resolution, the more information it contains.

Question 2

Charge-coupled device

Answer 2

Ccd. A screen covered by a million or more tiny silicon picture elements, each of which stores av electric charge when light falls on it. The image becomes recorded as a strings of numbers representing potential difference

Question 3

Scanning tunnelling microscope

Answer 3

Ultra sharp needle point scans surface. When close to atoms, electrons tunnel across the gap, resulting in an electric current. The current is maintained at a constant level by moving the needle up and down. This forms an image of the surface

Question 4

One bit

Answer 4

One choice - a 0 or a 1

Question 5

One byte

Answer 5

8 bits, giving 256 possibilities

Question 6

Number of alternatives =

Answer 6

2^number of bits. If the number of bits increases by one, the number of alternatives doubles.

Question 7

Number of bits =

Answer 7

log(2,number of alternatives)

Question 8

Removing noise

Answer 8

Replace each pixel with the median of its value and that of its 8 neighbours

Question 9

Smoothing sharp edges

Answer 9

Replace each pixel with that of the mean of it and its 8 neighbours - smooths our edges, but spreads noise around

Question 10

Finding edges

Answer 10

Subtract the N, S, E and W neighbouring pixels from 4x the pixel to enhance an edge - Laplace rule

Question 11

1/v =

Answer 11

1/u + 1/f WHERE U IS NEGATIVE