1. © Snapshot Science, 2011Snapshot Science KS4 Starter Pembrokeshire council in Wales is to start the first phase of turning off 14,000 street lights at night. Why would they want to do this? What objections might there be? Image: Peter Trimming geograph.org.uk

2. © Snapshot Science, 2011Snapshot Science KS4 Activity The council say it could save them at least £200 000 a year. Work out if this figure is accurate. Remember: Total cost = power x time x unit cost (kW) (h) (p) Information: There are 14 000 lights. Each light is on from midnight to 0530. One unit of electricity costs 10p The bulb in each light is 50 W. 1000 W = 1 kW

3. © Snapshot Science, 2011Snapshot Science KS4 Activity Total cost = power x time x unit cost (kW) (h) (p) Total cost = 0.05 x 5.5 x 10 (each light per day) Information: There are 14 000 lights. Each light is on from midnight to 0530. One unit costs 10p The bulb in each light is 50 W. 1000 W = 1 kW = 2.75p (£0.0275) Total cost = 0.00275 x 14 000 x 365 of all lights per year = £140 475 Not quite £200 000 How did the council reach this figure?