ACARA Digital Technologies Years 7–8 Definitions Worksheet: Representing Text, Images and Sound (Modules 153–172)
Name:
Date:
Class:
✎
Key terms
Write what each term means, in your own words.
1
eyedropper
2
24-bit colour
3
11111111 10000000 00000000
4
vector image
5
raster vs vector
6
waveform
7
sample
8
sample sequence
9
levels = 2^n
10
bit rate
Answer Key
ACARA Digital Technologies Years 7–8 · Modules 153–172 · Student wording will vary for definitions
1eyedropper — A tool that picks one pixel in an image and shows the red, green and blue numbers (0 to 255) stored for it, such as rgb(255, 0, 0) for pure red.
224-bit colour — Each pixel uses 8 bits for red, 8 for green and 8 for blue. That is 3 bytes (24 bits) per pixel, giving 256 x 256 x 256 = about 16.7 million possible colours.
311111111 10000000 00000000 — The RGB colour (255, 128, 0) written in binary. Each number becomes its own 8-bit byte for red, green and blue, and the three bytes are joined together to make one pixel.
4vector image — An image stored as shapes and paths (lines, curves) described by numbers and drawn when shown, not as a grid of pixels. It can scale up without pixelation. SVG is a common format.
5raster vs vector — Raster images store a colour number for every pixel and blur when enlarged; vector images store shape instructions and stay sharp at any size.
6waveform — A graph of a sound. Time runs left to right and volume goes up and down. Louder sounds make taller waves and silence is a flat line.
7sample — One measurement of a sound wave's volume at a single moment in time, stored as one whole number. Many samples taken at equal time steps are dots on the waveform.
8sample sequence — An ordered list of whole numbers, each measuring a sound's volume at a regular time. Plot them in order and join the dots to redraw an approximation of the wave.
9levels = 2^n — A sample resolution of n bits gives 2^n volume levels, so each extra bit doubles the levels. 8 bits give 256 levels and 16 bits give 65,536. Fewer levels means more rounding.
10bit rate — The number of bits used to store each second of sound: sample rate x sample resolution. A higher bit rate means better accuracy but more storage per second.