Science Formula Sheet
24 formulas across 4 chapters — with variables explained and exam tips where needed.
Ch 10Light — Reflection and Refraction(9 formulas)
Mirror formula
1/v + 1/u = 1/f
v = image distance, u = object distance, f = focal length
Use Cartesian sign convention: distances measured from pole, +ve in direction of incident light
Focal length and radius
f = R/2
R = radius of curvature
Magnification (mirror)
m = −v/u = h'/h
h' = image height, h = object height
m negative → real inverted image; m positive → virtual erect image
Lens formula
1/v − 1/u = 1/f
Magnification (lens)
m = v/u = h'/h
Lens maker's formula (simplified)
1/f = (n−1)[1/R₁ − 1/R₂]
n = refractive index
Refractive index
n = c/v = sin i / sin r
c = speed in vacuum, v = speed in medium, i = angle of incidence, r = angle of refraction
Power of lens
D (dioptre)P = 1/f
f in metres
Convex lens: +ve power; Concave lens: −ve power
Combined power
P = P₁ + P₂ + P₃ + ...
Ch 12Electricity(7 formulas)
Ohm's Law
V = IR
V = potential difference (V), I = current (A), R = resistance (Ω)
Resistance
R = ρL/A
ρ = resistivity, L = length, A = cross-section area
Resistors in series
R_total = R₁ + R₂ + R₃
Resistors in parallel
1/R_total = 1/R₁ + 1/R₂ + 1/R₃
Electric power
W (watt)P = VI = I²R = V²/R
Electrical energy
J or kWhE = Pt = VIt
1 kWh = 3.6 × 10⁶ J = 1 unit on electricity bill
Joule's law of heating
JH = I²Rt
Ch 1Chemical Reactions and Equations(4 formulas)
Law of conservation of mass
Total mass of reactants = Total mass of products
Combination reaction
A + B → AB
Decomposition reaction
AB → A + B
Double displacement
AB + CD → AD + CB
Ch 2Acids, Bases and Salts(4 formulas)
pH scale
pH < 7 = acidic, pH = 7 = neutral, pH > 7 = basic
Neutralisation
Acid + Base → Salt + Water
Action of acid on metal
Metal + Acid → Salt + Hydrogen gas
Action of base on non-metal oxide
Base + Non-metal oxide → Salt + Water