# Radiation and waves - Practical questions

During the GCSE Physics course you will complete practical activities from eight Practical Activity Groups (PAGs).

The exams will include questions about the apparatus, methods, safety precautions, results, analysis and evaluation of some of these experiments. You may also be asked to apply your knowledge to unfamiliar practical contexts, which will draw on your practical knowledge and understanding.

Practical questions will appear throughout both exams papers (Breadth and Depth), and at both Foundation Tier and Higher Tier.

Remember to look at your lab book or your notes from the practical activities you have done when you're revising for the exams.

There are four main aspects to 'Ideas about Science'. These are:

1. Planning practical experiments and investigations (including writing hypotheses and predictions, selecting apparatus and describing methods, controlling factors, and working safely).
2. Processing and analysing data (including doing calculations, presenting data graphically, identifying patterns and trends, evaluating results and experiments, and interpreting data to draw appropriate conclusions).
3. Developing scientific explanations (including ideas about correlation and cause, peer review, and the use of models in science).
4. The impacts of applications of science (including positive and negative impacts on people, other organisms and the environment, and ideas about risk and ethics).

## Sample question 1

A student is investigating refraction of light. They shine a light through a rectangular glass block at an angle. The diagram below shows the ray as it hits the glass block.

Question

a) Complete the diagram to show the path of the ray and label the angle of incidence and angle of refraction. [2 marks]

b) Fill in the gaps using some of the words below: [2 marks]

 smaller larger closer to further from

The light is now passed through a more dense material. This means the angle of refraction is ______, therefore ______ the normal.

OCR 21st Century Science, GCE Physics, PAG, February 2017.

a)

When drawing the refracted line, make sure you use a ruler. When the light passes into the glass, the speed decreases and therefore the ray will bend towards the normal. The angle of incidence is the angle between the ray going into the glass (the incident ray) and the normal. The angle of refraction is the angle between the refracted ray and the normal.

b) The light is now passed through a more dense material. This means the angle of refraction is smaller therefore closer to the normal.

As the density of an object increases, the speed the light will travel through it decreases, therefore bending the ray towards the normal. This means the angle will be smaller.

## Sample question 2

Question

A student is investigating waves using the equipment below:

She measures the length of ten waves on the viewing screen and calculates the average wavelength of one wave.

a) Why does this method only produce an 'estimated' wavelength? [2 marks]

b) Why is it more accurate to produce the ripples using a motor than by hand? [2 marks]

OCR 21st Century Science, GCE Physics, PAG, February 2017.

a) It is an estimate as you are measuring the image of the wave, rather than the wave itself.

When answering this question, read the context carefully and look at the equipment provided. You will see that you are using an image of the wave, rather than the wave itself to do the measurements. This makes them estimations.

b) Waves produced by the motor will all be the same and the time between each wave will stay constant. Human error is likely when producing waves by hand.

The key word in this question is accuracy, so, when answering the question, consider when the inaccuracies may lie when producing a wave by hand and how these are resolved by the motor.