Year 6 Science Light – Block 6L – Crime Lab Investigation

Session 2: Light travels in straight lines
Science curriculum area: Light / i) recognise that light appears to travel in straight lines
ii) use the idea that light travels in straight lines to explain that objects are seen because they give out or reflect light into the eye
iii) explain that we see things because light travels from light sources to our eyes or from light sources to objects and then to our eyes
Working Scientifically (UKS2) / i) planning different types of scientific enquiries to answer questions, including recognising and controlling variables where necessary
ii) recording data and results of increasing complexity using scientific diagrams and labels, classification keys, tables, scatter graphs, bar and line graphs
iii) reporting and presenting findings from enquiries, including conclusions, causal relationships and explanations of and degree of trust in results, in oral and written forms such as displays and other presentations
Teaching Objectives / ·  Demonstrate that light travels in straight lines
·  Understand why a light source is needed to see
Other curriculum areas / Maths
·  Recognise angles where they meet at a point or are on a straight line
·  Convert between standard units of measure
Teaching Objs / ·  Suggest viable angles based on sight
·  Convert feet and inches to cm
Key Vocabulary: light, light source, dark/darkness, reflect, reflective, direct/ direction, straight
Resources
CCTV based diagram including measurements, maths needed to solve the problem / Weblinks
http://www.bbc.co.uk/education/clips/zyntsbk - BBC Bitesize: Light travels in straight lines;
http://www.bbc.co.uk/education/clips/zf9c87h - BBC Bitesize: The human eye.
Whole Class: Have all experiment equipment ready and printed copies of the resources Explain to chn that the police believe that the school was 'cased' before being broken into - someone had visited the site prior to the crime. The evidence that they have for this is from internal and external CCTV recordings. The suspect was seen drilling a hole in the external gymnasium wall then shining a torch into the gym. Unfortunately the hole was refilled and covered perfectly and so cannot be located, but three spots of light were noted internally: one high up near the windows, one part way up the wall, and the third on the floor. The Crime Lab needs to know if light travels in straight lines or curves and believes if it is the former that with this information and the measurements of the internal walls that they can narrow down the height of the suspect to within a few centimetres. Look at the blank diagram with the chn and get them in pairs to decide if light travels in straight or curved lines. Then see if they can suggest the kind of angle the torch must have been held at and the position of the suspect (kneeling, stood straight, on tip toes) to match the internal spot positions. Ask chn how big they think the hole was and why (big enough to look through as well as shine the torch through - reinforce that light comes from a light source, not eyes (explain that the internal CCTV was pitch black when the torch was off). Explain that chn will need to calculate the height of the external hole from the diagram as well as calculate the height of the suspects in cm (we have only been given them in imperial measures). They also need to find a way to demonstrate that light travels in straight lines. Why might these things help eliminate one or more suspects? (Some may be too short to see through the hole at all three angles if light can only travel in straight lines).
Activities: Support chn in ability gps to calculate the height of the external hole and the height of the suspects in cm (see resource). Then give each gp a shoe box, torch, pen and knitting needles and ask them to see if they can demonstrate that light travels in straight (not curved) lines. Encourage chn to be creative and develop their own ideas, but in the knowledge that the knitting needles could be forced through a viewing hole to mark a point on the shoe box lid, which could then be marked by pen to test if the light from the torch hits the same point when shone at the same angle through the hole. Once they have concluded that light does travel in straight lines, get chn to calculate which suspect/s couldn’t have created and viewed the three beams (get chn to suggest likely angles of the torch and to think about eye height vs actual height and how much standing on tip toes adds to height).
Plenary / Come together and share conclusions - what science are we relying on: light travels in straight lines. What maths are we relying on - angles and conversions. Could the suspect have ‘cased’ the gymnasium without a light source? Why do we know that the hole must have been bigger than the size of an eye? (both the eye needed a visual and the light source needed to get through). Can chn explain how a light source works to enable us to see (reflection of light on our surroundings into our eyes)? Can the chn discount one of the suspects? (Prof Alice Nilsson who is 5ft 3.)
Outcomes / Children will
·  Demonstrate and conclude that light travels in a straight line
·  Know that a light source is needed in order to see
·  Convert feet and inches to cm
·  Make viable suggestions for given angles

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