4.5.6 Representing images, sound and other data

Question 1

What is a Bitmap Image made up of?

Answer 1

Bitmap images are made up of pixels.

Question 2

Define Pixel.

Answer 2

The smallest unit of an image, representing a single point with a specific colour and brightness.

Question 3

What is the equation for image file size?

Answer 3

image file size = colour depth x image height(px) x image width(px)

Question 4

What is Analogue Data?

Answer 4

Analogue is a continuous set of values.

Question 5

What is Digital Data?

Answer 5

Digital is a discreet set of values.

Question 6

Define Colour Depth.

Answer 6

A measure of the amount of colour used in an image, expressed in terms of the number of bits used to represent the colour of each pixel in an image.

Question 7

What is the number of colours that can be represented in a colour depth of 4? And how many bits are used?

Answer 7

2^4 = 16 colours
2^2 = 4, so 2 bits.

Question 8

Define Metadata.

Answer 8

Data related to the image file data itself. e.g width, height, colour depth

Question 9

Define Resolution.

Answer 9

A measure of the total number of pixels in an image, typically expressed in terms of the number of dots/pixels per inch.

Question 10

How do you add more colours to an image?

Answer 10

Add more bits per pixel.

Question 11

Define Sample Resolution.

Answer 11

The number of bits used to represent a single sample.

Question 12

Define Sampling Rate.

Answer 12

The numbers of samples taken per second/over a given period of time.
The frequency at which samples are taken.
On the x axis.

Question 13

Define Sound Sampling.

Answer 13

The process of converting analogue sound waves to a digital waveform, by storing a finite number of readings in binary.

Question 14

Define Audio Bit Depth.

Answer 14

The number of bits used to represent the amplitude of each audio sample, affecting the sound quality and dynamic range.
On the y axis.

Question 15

Define Amplitude.

Answer 15

The height of a sound wave, determining the loudness of the sound.

Question 16

Define Frequency.

Answer 16

The number of cycles of a sound wave per second, determining the pitch of the sound.

Question 17

Define Character Code.

Answer 17

The unique number used to represent a character.

Question 18

What is an Analogue to Digital Convertor used for?

Answer 18

Used to convert the sound waves to a digital format.

Question 19

What does the quality of the sound conversion depend on?

Answer 19

• sample interval
• sample resolution

Question 20

How does the sample rate affect quality?

Answer 20

The sample rate allows the measurement of the frequency of a wave. The more samples the more accurate the tone is.

Question 21

How does sample resolution affect quality?

Answer 21

The sample resolution allows the measurement of the amplitude of a wave. The higher the bit depth the more accurate it is.

Question 22

Describe the process of analogue to digital conversion.

Answer 22

1. Microphone (sensor) detects/ measures the analogue wave.
2. The sound wave is sampled at regular intervals.
3. For each sample the amplitude is measured.
4. This is converted into discrete binary values.
5. The values are stored in a sound file.

Question 23

Define Sampling Error.

Answer 23

When the sample of the amplitude is incorrect.