GCSE Questions - Electromagnetic Spectrum

Q1. A headline from a recent magazine article is shown below.

(a) Complete the following sentence. Skin cancer can be caused by exposure to excess ultraviolet rays from the Sun. (1 mark)

(b) Sunscreen should be used to protect your skin from the damaging effects of the Sun. A thick layer of sunscreen should be applied 30 minutes before sunbathing and re-applied every hour. The protection factor of a sunscreen lets you work out roughly how long you can stay in the Sun without causing damage to your skin. For example, a 'factor 10' sunscreen lets you stay in the Sun for up to ten times longer than if you were not using the sunscreen.

(i) Without sunscreen, a person with fair skin has found that she gets sunburn after 12 minutes of sunbathing. What is the maximum time that she could sunbathe without burning if she used 'factor 30' sunscreen on her skin? (1 mark)

12 minutes x 30 = 360 minutes

360 minutes (or 6 hours)

(ii) Why does the protection factor give only a rough idea of how long you can sunbathe without getting sunburn? (1 mark)

any one from:

sunscreen not applied thickly enough

sunscreen not applied often enough

sunscreen not applied half an hour before sunbathing

water reduces the protection factor

intensity of Sun depends on time of day/year or cloud cover

intensity of Sun depends on your location

The examiner did not accept answers in terms of different types of skin alone - although this IS a factor. That is because part three of the question related to this. Avoid putting down dulpicate information in answers. The examiner does not want you to use part of the question as an answer!

(iii) Another person has naturally dark skin. Suggest why he can sunbathe with less risk of getting skin cancer than a fair-skinned person. (2 marks)

More of the UV radiation is absorbed by the outer layers of dark skin because it has more melanin. This means that less UV penetrates deep into the skin where it can damage (living) cells / tissue.

If you used the words 'sunlight' or 'heat' instead of ultraviolet you got no marks for the question. It is not the heat (infra red) or light (visible - ROYGBIV) that causes the damage - it is ultraviolet which does not feel hot and cannot be seen!

(c) Most people know that sunbathing can cause skin cancer. But most holidaymakers still
like to come home with a suntan.
Why is it important that people understand that there are dangers involved in sunbathing? (1 mark)

So that people can make up their own minds about the potential risk to their health and be aware of how to take precautions.

No marks were awarded for 'They might get skin cancer'. Understanding that there is a danger doesn't prevent skin cancer. They need to take precautions - apply sunscreen.

(Total 6 marks)