The diagram shows an investigation at a primary school sports day. Fig. 1 shows two ultraviolet-sensitive beads placed in direct sunlight. One bead is cover...
Question 1 Report
The diagram shows an investigation at a primary school sports day. Fig. 1 shows two ultraviolet-sensitive beads placed in direct sunlight. One bead is covered by a clear plastic cap and the other is covered by a cap containing UV-blocking material. After five minutes, the unprotected bead changes colour strongly, while the bead under the UV-blocking cap changes colour only slightly. The student uses the result to discuss sun protection.
(a) State the part of the electromagnetic spectrum being investigated. [1]
(b) Explain why the bead with no cap changes colour more strongly. [2]
(c) Describe how the student could make this a fair comparison. [3]
(d) Explain one possible harmful effect of excessive ultraviolet radiation on human skin. [2]
(e) State two ways in which a person can reduce exposure to ultraviolet rays outdoors. [2]
Answer Details
(a) The radiation investigated is ultraviolet, UV. [1]
(b) With no cap, there is nothing to absorb or block the UV radiation. [1] More UV reaches the bead, so it produces a greater colour change. [1]
(c) A fair comparison controls all variables except whether the cap blocks UV. Use identical beads, expose both for the same time, and put them in the same position and direction. [3] Carrying out both tests at the same time, and using equal-sized caps that differ only in UV-blocking material, are also valid controls.
(d) Excessive UV can damage cells or DNA in skin. [1] This can cause sunburn, premature ageing, or increase the risk of skin cancer. [1]
(e) Two ways are to apply sunscreen and wear covering clothing or a hat. [2] Staying in shade, wearing UV-blocking sunglasses, and avoiding strong midday sunlight are also acceptable.
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