dcf.cymru stimulus sheet · Science · Year 9
Ysgol Cwm Dyfnant, its staff, its pupils and the photo folder are invented. The file sizes, the storage allowance and the image measurements are invented but realistic. The typical cell sizes in section 4 are real, rounded values.
From: Mrs Elen Morgan, Head of Science
To: Year 9 science classes
Subject: Microscope photos from 9C
Last week 9C looked at cells under the microscope and took photos with the microscope camera. The photos are all in one folder called Y9 microscope stuff, and that folder is only on the prep room laptop. If the laptop breaks, we lose everything. Nobody can tell from the names what most of the photos show.
I want to move the photos to the school’s cloud storage on Hwb so that every Year 9 pupil can use them for revision, and so we can add next year’s photos. Before I do, I need a naming rule, a folder plan, sharing rules and a back-up plan. I also want the real size of the cells worked out, so the photos can be used in lessons. Over to you.
Folder: Y9 microscope stuff on the prep room laptop. Sizes are as the laptop shows them.
| File | Current name | Date taken | Size |
|---|---|---|---|
| A | IMG_0042.jpg | 15 September 2026 | 3.6 MB |
| B | IMG_0042 (1).jpg | 15 September 2026 | 3.6 MB |
| C | final final.jpg | 15 September 2026 | 3400 kB |
| D | cheek cells EDITED copy.jpg | 15 September 2026 | 3500 kB |
| E | onion GOOD.jpg | 15 September 2026 | 3.8 MB |
| F | leaf.jpg | 16 September 2026 | 3.7 MB |
| G | IMG_0051.jpg | 16 September 2026 | 3.5 MB |
| H | blurry dont use.jpg | 16 September 2026 | 2900 kB |
| I | Screenshot 2026-09-16 103412.png | 16 September 2026 | 8.2 MB |
| J | cheek cells Dafydd group 3.jpg | 15 September 2026 | 3.3 MB |
Each group wrote down what they photographed. The image measurement is the length of the feature on the full-size photo, measured by the group with the on-screen ruler. Every eyepiece lens in the lab is ×10.
| File | What it shows | Eyepiece | Objective | Group | Image measurement |
|---|---|---|---|---|---|
| A | Onion epidermis, stained with iodine | ×10 | ×10 | 2 | One cell is 25 mm long |
| B | Exactly the same picture as A | ×10 | ×10 | 2 | None |
| C | Cheek cells, stained with methylene blue | ×10 | ×40 | 1 | One cell is 24 mm across |
| D | Photo C with labels drawn on: nucleus, cytoplasm, cell membrane. Edited on 16 September. | ×10 | ×40 | 1 | None |
| E | Onion epidermis, stained with iodine | ×10 | ×40 | 3 | One nucleus is 6 mm across |
| F | Canadian pondweed (Elodea) leaf cells, no stain | ×10 | ×40 | 4 | One cell is 40 mm long. One chloroplast is 2 mm across. |
| G | Onion epidermis, the same slide as A | ×10 | Not written down | 2 | One cell is 10 mm long |
| H | Cheek cells, completely out of focus | ×10 | ×10 | 4 | None |
| I | A photo of group 4 crowded round the microscope. Four pupils’ faces are clearly visible. | None | None | 4 | None |
| J | Cheek cells, stained with methylene blue | ×10 | ×10 | 3 | None |
| Topic | Facts |
|---|---|
| Total magnification | Total magnification = eyepiece magnification × objective magnification. Example: ×10 eyepiece and ×4 objective gives ×40. |
| Magnification formula | magnification = image size ÷ actual size actual size = image size ÷ magnification image size = actual size × magnification Image size and actual size must be in the same unit. |
| Small lengths | 1 mm = 1000 micrometres (µm). To change mm to µm, multiply by 1000. |
| Typical sizes (real, approximate) | Human cheek cell: about 60 µm across. Onion epidermal cell: about 200 to 300 µm long. Plant cell nucleus: about 10 to 20 µm. Chloroplast: about 5 µm. |
| Storage units | Each pixel of a colour photo needs 3 bytes (1 byte each for red, green and blue). On this sheet: 1 kB = 1000 bytes, 1 MB = 1000 kB, 1 GB = 1000 MB. (Some computers count in 1024s instead. We use 1000s throughout.) |
| The microscope camera | 12 megapixels (12 000 000 pixels). It saves each photo as a compressed JPEG of about 3.6 MB (invented typical size). |
| Storage allowance | The school has set aside 2 GB of Hwb cloud storage for science microscope photos (invented). Each year there are 8 Year 9 classes. Each class has 4 groups, and each group takes about 5 photos (invented). |
| View and edit | View: can open and download a file but cannot change it. Edit: can change, rename, move and delete it. |
| The 3-2-1 back-up rule | Keep 3 copies of anything important, on 2 different types of storage, with 1 copy off-site (somewhere other than the school building, for example the cloud). |
| School rules for images | Images shared with pupils must not show pupils’ faces, and file names must not contain pupils’ names. Share only with school (Hwb) accounts, never “anyone with the link”. |