Class 10 Physics – Chapter 1 & 2 Formulas
Chapter 1: Reflection & Refraction (Light)
Concept Formula / Relation
Law of Reflection ∠ incidence = ∠ reflection
Mirror: radius & focal length R = 2f
Mirror formula 1/v + 1/u = 1/f
Magnification (mirror) m = h_i / h_o = -v/u
Refraction (Snell’s law) n■ sin i = n■ sin r
Refractive index µ = speed in vacuum / speed in medium
Lens formula 1/v - 1/u = 1/f
Magnification (lens) m = h_i / h_o = v/u
Power of lens P = 1/f (f in metres, P in dioptres)
Chapter 2: Electricity
Quantity Formula / Relation
Electric current I=Q/t
Potential difference V=W/Q
Ohm’s Law V = IR
Resistance (geometry) R=ρl/A
Series resistors R_eq = R1 + R2 + ...
Parallel resistors 1/R_eq = 1/R1 + 1/R2 + ...
Electric power P = VI = I²R = V²/R
Heat produced H = I²Rt = VIt = V²t/R
Chapter 1: Reflection & Refraction (Light)
Concept Formula / Relation
Law of Reflection ∠ incidence = ∠ reflection
Mirror: radius & focal length R = 2f
Mirror formula 1/v + 1/u = 1/f
Magnification (mirror) m = h_i / h_o = -v/u
Refraction (Snell’s law) n■ sin i = n■ sin r
Refractive index µ = speed in vacuum / speed in medium
Lens formula 1/v - 1/u = 1/f
Magnification (lens) m = h_i / h_o = v/u
Power of lens P = 1/f (f in metres, P in dioptres)
Chapter 2: Electricity
Quantity Formula / Relation
Electric current I=Q/t
Potential difference V=W/Q
Ohm’s Law V = IR
Resistance (geometry) R=ρl/A
Series resistors R_eq = R1 + R2 + ...
Parallel resistors 1/R_eq = 1/R1 + 1/R2 + ...
Electric power P = VI = I²R = V²/R
Heat produced H = I²Rt = VIt = V²t/R
