How to play Magnification Challenge
Magnification Challenge is a free GCSE biology game about the magnification formula. Each question gives you two of three values: the size of the image, the real size of the object and the magnification. You use the formula to find the missing one, then pick it from four options.
The first three questions use one unit throughout, so you only need the formula. The next four give the image size and the real size in different units, such as millimetres and micrometres. You convert one of them before you divide. The last three bring in standard form, and one of them shows a scale bar in place of a real size. Tick the harder start to begin with the unit questions.
The clock counts down from 15 seconds. A right answer scores 10 points, and you get 5 more if you answer before the clock runs out. A wrong answer scores nothing. After every answer the game shows the formula it used and the right answer. The practice switch hides the clock and the bonus.
The science behind the magnification formula
A microscope makes a small object look bigger. Magnification tells you how many times bigger the image is than the real object. AQA prints the formula as a fraction: magnification = size of image ÷ size of real object. You can rearrange it to find the image size (magnification × real size) or the real size (image size ÷ magnification).
Both sizes must be in the same unit before you divide. Cells are tiny, so biologists use small units. A millimetre (mm) is a thousandth of a metre, a micrometre (µm) is a millionth and a nanometre (nm) is a billionth. Edexcel names these as the prefixes milli (10⁻³), micro (10⁻⁶) and nano (10⁻⁹). So 1 mm is 1,000 µm, and 1 µm is 1,000 nm.
Magnification has no unit, because the two units cancel when you divide. A magnification of 500 means the image is 500 times bigger than the object. Large answers are easier to read in standard form, so 200,000 becomes 2 × 10⁵. AQA asks students to give answers in standard form where it fits. Edexcel puts calculations in standard form in its Higher tier.
A scale bar is a line on the image with its real length written beside it. Measure the bar, work out the magnification from it, then use that to find the real size of the object. One easy slip is to give the length of the scale bar as the answer.
The formula is in AQA 8461 and 8464 at 4.1.1.5. Edexcel 1BI0 and 1SC0 cover the units in 1.5 and magnification calculations in the core practical at 1.6. OCR J247 includes the calculation of magnification in B1.1a. Of these, only AQA prints the formula itself. Magnification is not part of KS3 science.
Tips for using the magnification formula
- Write the formula first. Cover the value you want, and the other two show whether to multiply or divide.
- A microscope image is bigger than the object, so the magnification is more than 1. A tiny decimal means you divided the wrong way round.
- Convert before you divide. Putting both sizes in the smaller unit avoids decimals.
- Each step from mm to µm to nm multiplies by 1,000. Going back the other way divides by 1,000.
- Give a magnification with no unit. An image size or a real size always needs one.
In a scale bar question, find the magnification from the bar first. Then use it on the object you want to measure.
Use this in the classroom
Magnification Challenge suits Years 9 to 11 while you teach microscopy, or just before a practical where students look at cells under a microscope. It also works after the practical, when students have measured a drawing and need to turn that length into a real size.
Work through the first three questions together on the board. Ask students to write the formula and cover the unknown before anyone chooses. For the unit questions, ask each student to convert both sizes on a mini whiteboard first. The wrong options come from real slips, such as dividing the wrong way round or skipping the conversion, so a wrong pick is a good place to start a discussion.
The scale bar question works well at the end of a lesson. Draw a bar on the board, label its real length and ask the class to find the size of a cell drawn next to it. For more work on units, Unit Sprint gives quick practice at converting them.
The practice switch removes the clock for students who want more time. The page for teachers has more ideas, and the page for parents explains how the site works.
Similar games
Build the cells you have been measuring in Cell Builder. To practise rearranging other formulas, try Equation Rearranger, which uses physics equations. The all games page has every game on the site.
Questions people ask
Students and teachers often ask these questions about magnification.
What is the formula for magnification?
Magnification = image size ÷ real size. To find the image size, multiply the magnification by the real size. To find the real size, divide the image size by the magnification. Use the same unit for both sizes.
How do you convert mm to µm for magnification?
Multiply by 1,000, because 1 mm is 1,000 µm. To go from µm to nm, multiply by 1,000 again. So 2 mm is 2,000 µm, and 2 µm is 2,000 nm.
Does magnification have a unit?
No. You divide one length by another, so the units cancel. Write a magnification as a plain number, such as 400.
How do I use a scale bar to find the real size of a cell?
Measure the scale bar on the image and read the real length written beside it. Put both in the same unit, then divide the measured length by the real length to get the magnification. Then divide the length of the cell on the image by that magnification.