The equation that relates the optical power of a lens to its focal length is:
power (in dioptres)=1focal length (in metres) \text{power (in dioptres)} = \frac{1}{\text{focal length (in metres)}} power (in dioptres)=focal length (in metres)1The optical power of a magnifying glass lens is +6.25 dioptres+6.25\text{ dioptres}+6.25 dioptres.
Use the equation to calculate the focal length of this lens in cm\text{cm}cm.
24 exam-style questions on Edexcel GCSE Physics 5.1 Reflection, refraction and lenses (physics only). Each one has a worked solution and a mark scheme showing where the marks go.