This exam tips covers Exam Tips - Images & Sound within Images & Sound for GCSE Computer Science. Revise Images & Sound in 3.3 Data Representation for GCSE Computer Science with 18 exam-style questions and 16 flashcards. This topic shows up very often in GCSE exams, so students should be able to explain it clearly, not just recognise the term. It is section 10 of 12 in this topic. Treat this as a marking guide for what examiners are looking for, not just a fact list.
Exam Tips - Images & Sound
Most common exam questions:
- "Calculate image file size" → Width × Height × Color Depth ÷ 8
- "Calculate sound file size" → Sample Rate × Bit Depth × Duration × Channels ÷ 8
- "What is a pixel?" → Smallest unit of a digital image (picture element)
- "What is sample rate?" → Number of samples per second (Hz)
- "Higher sample rate = ?" → Better quality but larger file
Image calculation tips:
- Always multiply: Width × Height × Color Depth
- Don't forget to divide by 8 to convert bits → bytes
- Watch out for units: KB, MB, or bytes?
- 24-bit color = True Color (most common)
Sound calculation tips:
- Four factors: Sample Rate × Bit Depth × Duration × Channels
- Stereo = ×2 channels (don't forget!)
- Duration must be in seconds
- Divide by 8 for bytes
- CD quality = 44,100 Hz, 16-bit, stereo
Common mistakes to avoid:
- Forgetting to divide by 8 (bits → bytes)
- Missing "× channels" for stereo sound
- Confusing width/height order
- Not converting duration to seconds
- Mixing up sample rate (Hz) with bit depth (bits)
Practice questions for Images & Sound
What does colour depth refer to in a digital image?
Explain the effect of increasing colour depth on a digital image. Refer to both file size and image quality in your answer.