Recent posts View all
Home of real teaching & learning
  • Full support for teachers
  • Focus on critical thinking
  • Engaging classroom activities
  • Integrated student eBook
  • Assessed tasks / qBank
  • Practice exam questions

The InThinking Guarantee: Our sites are written by expert practitioners and not by AI

See our AI policy

Disclaimer: InThinking subject sites are neither endorsed by nor connected with the International Baccalaureate Organisation.

Don't miss out, find out!
IB Approved Workshops
Physics
IB DP Category 1

Paris, France, 13 - 15 November 2026

Find out more
Physics: A focus on the experimental programme
IB DP Category 3

Paris, France, 19 - 21 February 2027

Find out more
Physics
IB DP Category 2

Berlin, Germany, 26 - 28 February 2027

Find out more
Virtual Think-Ins

Find all InThinking events at
inthinking.net

Solar grill part 2

It's a lot of mirrors!

The problem is getting them to align so that they all reflect the sunlight to the same spot. I can already tell that this isn't going to happen but it is interesting to consider why the light has to be focussed on one point in order to boil water. Why can't we simply place a cup of water in the sun. Well a cup does not have a very big surface area so wouldn't absorb much energy. So, how about increasing the area so that the water was in a shallow dish. The problem then is the heat loss. The maximum temperature is reached when the energy absorbed = the energy radiated and the energy radiated depends on the surface area. So a big shallow dish would absorb a lot of energy but would radiate a lot too. By focussing the light we put a lot of energy into a small area. If the area of the mirror is 1m2 then we would be shining 1 kW of power onto the focal point.

Help