OCR J277 Mark Scheme

OCR	GCSE (9-1) Computer Science Mark Scheme J277/01: Unit 1.2 Images

Question	Answer	Marks	Guidance
1a	The smallest addressable element (or part/unit) of an image (1) OR A single point of colour in an image (1)	1	AO1 (Knowledge) Examiner Note: Do NOT accept "A square on the screen" (too vague). Do NOT accept "Smallest part of a screen" (that is a hardware pixel, not an image pixel).
1b	The width (in pixels) multiplied by the height (in pixels) (1) OR The number of pixels in the image (1)	1	AO1 (Knowledge) Accept "Concentration of pixels". Accept "Height x Width".
1c	The number of bits stored per pixel (1)	1	AO1 (Knowledge) Must link "bits" to "pixel".
2a	Working: 100 x 100 x 2 (1) Answer: 20,000 (bits) (1)	2	AO2 (Application) Formula is Height x Width x Colour Depth. Answer only gets full marks. If they calculate bytes (2500) but unit line says "bits", award 1 mark for working.
2b	4 (colours)	1	AO2 (Application) 2² = 4. Common error is saying "2 colours".
3a	The file size will increase (1) Because more bits are being used to represent each pixel (1)	2	AO1 (Knowledge) Must explain why (bits per pixel). Accept "File size will be 3 times larger" (8 to 24).
3b	The quality/appearance will look more realistic (1) Because more colours / shades are available to be used (1)	2	AO1 (Knowledge) Examiner Note: Do NOT accept "The resolution increases" or "It is clearer/sharper". Colour depth affects colour accuracy, not sharpness/resolution.
4a	Height (in pixels) / Width (in pixels) / Colour Depth / Resolution / File Type / Date Created / GPS Location	2	AO1 (Knowledge) Award 1 mark per valid item. Do not accept "The image data" or "The binary".
4b	It tells the computer how to reconstruct the binary data into an image (1) OR Without it, the computer wouldn't know the width/height (where to start a new line of pixels) (1)	2	AO1 (Knowledge) Accept specific examples: "It tells the computer how many bits represent one pixel."
5	3 (MB)	1	AO2 (Application) J277 allows division by 1000 (3,000,000 / 1000 / 1000). Must use 1000. 2.86 (1024) is no longer accepted for this resource.
6	The 10-megapixel image has a higher resolution / more pixels (1) This means the pixels are smaller (for the same physical size) / pixel density is higher (1) So the image shows finer detail / is less pixelated (1)	3	AO2 (Application) Max 3 marks. Must link "More pixels" -> "Smaller pixels/Higher density" -> "Better detail".