1
\mathrm{m}=\frac{\mathrm{h}_{\mathrm{i}}}{\mathrm{h}_{\mathrm{o}}}
2
\mathrm{m}=-\frac{\mathrm{v}}{\mathrm{u}}
3
\mathrm{P}=\frac{1}{\mathrm{f}}
4
\frac{1}{\mathrm{v}}-\frac{1}{\mathrm{u}}=\frac{1}{\mathrm{f}}
FORMULA CHAPTER
Chapter 05 – Refraction Through a Lens
ICSEClass 10Physics4 formulas
Complete ICSE Class 10 Chapter 05 lens formulas covering focal length, lens formula, magnification and power of a lens.
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Linear Magnification Using Heights
\mathrm{m}=\frac{\mathrm{h}_{\mathrm{i}}}{\mathrm{h}_{\mathrm{o}}}
Worked example
Given: hi = -6 cm, ho = 2 cm Calculation: m = -6/2 Answer: m = -3
Linear Magnification Using Distances
\mathrm{m}=-\frac{\mathrm{v}}{\mathrm{u}}
Worked example
Given: v = -30 cm, u = -15 cm Calculation: m = -(-30)/(-15) Answer: m = -2
Power of a Lens
\mathrm{P}=\frac{1}{\mathrm{f}}
SymbolMeaningUnit
PPower of lensD
fFocal lengthm
Worked example
Given: f = 0.5 m Calculation: P = 1 / 0.5 Answer: P = 2 D
Lens Formula
\frac{1}{\mathrm{v}}-\frac{1}{\mathrm{u}}=\frac{1}{\mathrm{f}}
SymbolMeaningUnit
uObject distancem or cm
vImage distancem or cm
fFocal lengthm or cm
Worked example
Given: u = −30 cm, f = 15 cm Calculation: 1/v = 1/f + 1/u = 1/15 − 1/30 Answer: v = 30 cm