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. Choose Challenge 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.

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.

• 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.