State the equation for Momentum (p), the Law of Conservation of Momentum, and how crumple zones/seatbelts reduce injury using F = Δp / Δt.

Momentum: p = mv (in kg m/s). In a closed system, total momentum before an event equals total momentum after an event. Since Force = Rate of change of momentum (F = mΔv / Δt), seatbelts, airbags, and crumple zones increase the time taken (Δt) for the passenger's momentum to reach zero, which decreases the impact force acting on the passenger.

Define Specific Heat Capacity (c), state its equation, and explain how to measure it experimentally (GCSE Required Practical).

Specific heat capacity is the energy required to raise the temperature of 1 kg of a substance by 1°C: ΔE = mcΔθ. Experiment: place an electric immersion heater and thermometer into an insulated 1 kg metal block, measure current (I), potential difference (V), and time (t) to find E = VIt, plot temperature vs time, and calculate c = E / (mΔθ).

Distinguish between radioactive contamination and irradiation, and compare nuclear fission with nuclear fusion (Triple Science).

Irradiation is exposing an object to nuclear radiation without touching the source (does not make the object radioactive); contamination is the unwanted presence of radioactive atoms on or inside an object. Nuclear fission is the splitting of a large unstable nucleus (e.g., Uranium-235) after absorbing a slow neutron, releasing 2–3 neutrons and energy; nuclear fusion is joining two light nuclei (e.g., hydrogen isotopes) at extreme temperature/pressure to form a heavier nucleus (Helium).

State the four key kinematics equations for uniform acceleration in GCSE Physics and explain how to interpret distance–time and velocity–time graphs.

1) v = s / t; 2) a = (v − u) / t; 3) v² − u² = 2as. On a distance–time graph, the gradient equals speed. On a velocity–time graph, the gradient equals acceleration and the area under the graph equals displacement (distance travelled).

State Newton's First, Second, and Third Laws of Motion.

First Law: If the resultant force on an object is zero, a stationary object stays stationary and a moving object continues at the same velocity. Second Law: Resultant force is directly proportional to acceleration and inversely proportional to mass: F = ma. Third Law: Whenever two objects interact, they exert equal and opposite forces of the same type on each other.

What are the wire colours, potentials, and safety functions inside a standard UK three-pin mains plug (230 V, 50 Hz AC)?

Live wire (Brown): carries alternating potential at 230 V (connected to the fuse). Neutral wire (Blue): completes the circuit and is held at or near 0 V. Earth wire (Green and yellow stripes): at 0 V, connected to the metal casing of the appliance to provide a low-resistance path to earth if the live wire touches the case, blowing the fuse.

State the Transformer Equations (Vp/Vs = np/ns and VpIp = VsIs) and distinguish between an alternator (AC) and a dynamo (DC) (Triple Science).

Transformer voltage ratio: Vp / Vs = np / ns. For a 100% efficient transformer: Vp × Ip = Vs × Is. Both alternators and dynamos use electromagnetic induction (generator effect): an alternator uses slip rings and brushes to produce alternating current (AC), whereas a dynamo uses a split-ring commutator to produce direct current (DC).

How do alpha decay and beta-minus decay alter the mass number (A) and atomic number (Z) of an unstable nucleus?

In Alpha (α) decay, the nucleus emits ⁴₂He, so mass number decreases by 4 (A − 4) and atomic number decreases by 2 (Z − 2). In Beta-minus (β⁻) decay, a neutron changes into a proton and emits ⁰₋₁e, so mass number stays the same (A) and atomic number increases by 1 (Z + 1).

Explain why the National Grid uses step-up and step-down transformers to transmit electrical power across the country.

Step-up transformers increase potential difference to ~400,000 V, which decreases the transmission current (since P = VI). Because power wasted due to heating in the cables is P_loss = I²R, a smaller current vastly reduces energy lost as heat, increasing efficiency. Step-down transformers then reduce p.d. to 230 V for safe domestic use.

List the 7 regions of the Electromagnetic Spectrum in order of increasing frequency (decreasing wavelength) and state one use for each.

Radio waves (TV/radio broadcasting) → Microwaves (satellite communications, cooking food) → Infrared (thermal imaging, remote controls, heaters) → Visible light (fibre optic communications, photography) → Ultraviolet (fluorescent lamps, sterilising water) → X-rays (medical bone imaging) → Gamma rays (sterilising medical equipment, radiotherapy for cancer).

How does a simple DC electric motor keep rotating continuously in one direction?

Opposite sides of the current-carrying rectangular coil carry current in opposite directions inside a magnetic field, experiencing equal and opposite forces (up on one side, down on the other) that create a turning moment. A split-ring commutator reverses the direction of the current around the coil every half-turn so the coil continues rotating in the same direction.

Trace the life cycle of a solar-mass star vs a massive star, and explain how Red-Shift provides evidence for the Big Bang (Triple Science).

Nebula → Protostar → Main Sequence Star (hydrostatic equilibrium). Solar-mass star → Red Giant → White Dwarf → Black Dwarf. Massive star → Red Supergiant → Supernova → Neutron Star or Black Hole. Red-shift: light from distant galaxies is shifted to longer wavelengths, showing galaxies are receding and the universe is expanding from an initial hot, dense state (Big Bang).

Explain why a skydiver reaches terminal velocity in terms of resultant forces.

Initially, weight (downwards) is much greater than air resistance (upwards), so there is a large downward resultant force and the skydiver accelerates. As speed increases, air resistance increases until air resistance equals weight. At this point, the resultant force is zero, so acceleration is zero and the skydiver falls at constant terminal velocity.

Define radioactive half-life (t₁/₂) and calculate the remaining activity of a 640 Bq sample after 3 half-lives.

Half-life is the average time taken for the number of undecayed radioactive nuclei in a sample (or the count rate/activity) to halve. After 3 half-lives: 640 → 320 → 160 → 80 Bq (or 640 × (½)³ = 80 Bq; net decline ratio is 1/8).

Define Stopping Distance, Thinking Distance, and Braking Distance, and list factors that increase each.

Stopping Distance = Thinking Distance + Braking Distance. Thinking distance (distance travelled during driver's reaction time) is increased by alcohol/drugs, tiredness, distractions, and higher speed. Braking distance (distance travelled under braking force) is increased by icy/wet roads, worn tyres/brakes, heavy vehicle mass, and higher speed (since Ek = ½mv², doubling speed quadruples braking distance).

Compare Alpha (α), Beta (β⁻), and Gamma (γ) nuclear radiation in terms of nature, charge, range in air, penetrating power, and ionising power.

Alpha (α): Helium nucleus (2p + 2n), +2 charge, ~5 cm range in air, stopped by paper/skin, strongly ionising. Beta (β⁻): Fast-moving electron emitted when a neutron turns into a proton, -1 charge, ~1 m range in air, stopped by ~5 mm aluminium, moderately ionising. Gamma (γ): High-frequency electromagnetic wave, 0 charge, infinite range in air, reduced by thick lead/concrete, weakly ionising.

What is Specific Latent Heat (L), what is its equation, and why does temperature remain constant during a change of state?

Specific latent heat is the energy required to change the state of 1 kg of a substance with no change in temperature: E = mL (L_f = latent heat of fusion for solid↔liquid; L_v = latent heat of vaporisation for liquid↔gas). During a state change, energy is used to overcome (or form) intermolecular forces of attraction rather than increasing average kinetic energy (temperature).

Distinguish between scalar and vector quantities with 3 examples of each, and state the equation for Weight.

Scalars have magnitude only (mass, speed, distance, energy, time). Vectors have both magnitude and direction (weight/force, velocity, displacement, acceleration, momentum). Weight (N) = Mass (kg) × Gravitational field strength (N/kg): W = mg.

State Hooke's Law, define the limit of proportionality, and distinguish between elastic and inelastic deformation.

Hooke's Law: The extension of an elastic object (like a spring) is directly proportional to the force applied, provided the limit of proportionality is not exceeded: F = ke. Elastic deformation means the object returns to its original length when the force is removed; inelastic (plastic) deformation means it remains permanently stretched.

Compare the rules for current (I), potential difference (V), and total resistance (R) in series vs parallel circuits.

Series circuit: Current is the same everywhere (I1 = I2); total p.d. is shared across components (Vtotal = V1 + V2); total resistance is the sum (Rtotal = R1 + R2). Parallel circuit: p.d. across each branch is equal to the supply p.d. (V1 = V2); total current splits between branches (Itotal = I1 + I2); adding a resistor in parallel DECREASES total resistance.

State the density equation and explain how to measure the density of an irregular solid object (GCSE Required Practical).

Density: ρ = m / V (in kg/m³ or g/cm³). For an irregular solid: 1) Measure its mass (m) using a digital top-pan balance; 2) Fill a Eureka (displacement) can with water up to the spout, submerge the object completely, and collect the displaced water in a measuring cylinder to find the exact volume (V); 3) Calculate ρ = m / V.

State the GCSE Physics equations for Kinetic Energy (Ek), Gravitational Potential Energy (Ep), and Elastic Potential Energy (Ee).

Kinetic energy: Ek = ½mv² (m = mass in kg, v = speed in m/s). Gravitational potential energy: Ep = mgh (m = mass in kg, g = gravitational field strength in N/kg, h = height in m). Elastic potential energy: Ee = ½ke² (k = spring constant in N/m, e = extension in m).

How does a convex (converging) lens differ from a concave (diverging) lens, and what is the lens magnification formula (Triple Science)?

A convex lens bulges outwards and converges parallel light rays to a principal focus (can form real or virtual images). A concave lens curves inwards and diverges parallel rays so they appear to come from a principal focus (always forms a diminished, upright, virtual image). Magnification = Image height ÷ Object height.

Compare transverse and longitudinal waves with examples, and state the Wave Equation and Period Equation.

Transverse waves: oscillations are perpendicular to the direction of energy transfer (all electromagnetic waves, water ripples, S-waves). Longitudinal waves: oscillations are parallel to the direction of energy transfer, forming compressions and rarefactions (sound waves, ultrasound, P-waves). Wave speed: v = fλ; Period: T = 1 / f.

Use the particle model of gases to explain why heating a fixed volume of gas increases its pressure, and state Boyle's Law.

Heating a gas increases the average kinetic energy and speed of the gas molecules. They collide with the container walls more frequently and with greater force per collision, producing a greater force per unit area (higher pressure). At constant temperature (Boyle's Law): Pressure × Volume = constant (pV = constant).

State the core GCSE Electricity equations linking Charge (Q), Current (I), Time (t), Potential Difference (V), Energy (E), Resistance (R), and Electrical Power (P).

1) Q = I × t (Charge in Coulombs = Current in Amps × Time in seconds); 2) E = Q × V (Energy in Joules = Charge × Potential difference in Volts); 3) V = I × R (Ohm's Law); 4) P = V × I and P = I² × R.

What is the Motor Effect, how do you use Fleming's Left-Hand Rule, and what is the equation F = BIl (Higher Tier)?

When a current-carrying wire is placed inside a magnetic field, their magnetic fields interact to exert a force on the wire: F = B × I × l (Force in N = Magnetic flux density in Tesla × Current in Amps × Length of wire in m). Fleming's Left-Hand Rule: Thumb = Force (Motion), First finger = Magnetic Field (N to S), Second finger = Conventional Current (+ to -).

Explain why a light ray bends towards the normal when entering a denser medium (refraction) using wavefronts.

When a wave enters an optically denser medium (e.g., air into glass) at an angle, one side of the wavefront enters the glass first and slows down while the other side continues faster in air. This causes the wavefront to pivot and bend towards the normal (wavelength decreases while frequency stays constant).

State the equations for Moments, Levers, and Pressure in Solids and Liquids (Triple Science).

Moment of a force: M = F × d (Force in N × perpendicular distance from pivot in m; in equilibrium, total clockwise moment = total anticlockwise moment). Solid pressure: p = F / A (in Pascals, Pa = N/m²). Liquid pressure at depth h: p = hρg.

State the equations for Power (P), Work Done (W), and Efficiency.

Power: P = E / t = W / t (in Watts, W = J/s). Work Done: W = F × s (Force in N × distance moved in the direction of force in m). Efficiency = Useful output energy transfer ÷ Total input energy transfer (or Useful power output ÷ Total power input).

Describe and explain the current-potential difference (I–V) characteristics of an ohmic resistor, a filament lamp, and a semiconductor diode.

Ohmic resistor (at constant temperature): straight line through the origin (I ∝ V, constant resistance). Filament lamp: S-shaped curve flattening at high V—as current increases, the metal filament gets hotter, metal ions vibrate more, colliding more with electrons and increasing resistance. Diode: current flows in one direction only above ~0.6 V (very high resistance in reverse).

How does the resistance of a thermistor and an LDR (Light Dependent Resistor) change with temperature and light intensity?

For an NTC thermistor, as temperature increases, its resistance decreases (used in thermostats). For an LDR, as light intensity increases, its resistance decreases (used in automatic street lights).

GCSE Physics Paper 1 & 2: Energy, Electricity, Particle Model, Atomic Radioactivity, Forces, Waves & Magnetism

Essential GCSE and IGCSE Physics revision covering energy stores and equations, IV characteristics, series/parallel circuits, specific heat capacity, nuclear alpha/beta/gamma decay, Newton's laws, momentum, electromagnetic spectrum, and the motor/generator effects.

Level: intermediate
Languages: en → en
Cards: 32
Markdown: GCSE Physics Paper 1 & 2: Energy, Electricity, Particle Model, Atomic Radioactivity, Forces, Waves & Magnetism (.md)

Flashcards (32)

#	Front (Term / Question)	Back (Definition / Answer)
1	State the equation for Momentum (p), the Law of Conservation of Momentum, and how crumple zones/seatbelts reduce injury using F = Δp / Δt.	Momentum: p = mv (in kg m/s). In a closed system, total momentum before an event equals total momentum after an event. Since Force = Rate of change of momentum (F = mΔv / Δt), seatbelts, airbags, and crumple zones increase the time taken (Δt) for the passenger's momentum to reach zero, which decreases the impact force acting on the passenger.
2	Define Specific Heat Capacity (c), state its equation, and explain how to measure it experimentally (GCSE Required Practical).	Specific heat capacity is the energy required to raise the temperature of 1 kg of a substance by 1°C: ΔE = mcΔθ. Experiment: place an electric immersion heater and thermometer into an insulated 1 kg metal block, measure current (I), potential difference (V), and time (t) to find E = VIt, plot temperature vs time, and calculate c = E / (mΔθ).
3	Distinguish between radioactive contamination and irradiation, and compare nuclear fission with nuclear fusion (Triple Science).	Irradiation is exposing an object to nuclear radiation without touching the source (does not make the object radioactive); contamination is the unwanted presence of radioactive atoms on or inside an object. Nuclear fission is the splitting of a large unstable nucleus (e.g., Uranium-235) after absorbing a slow neutron, releasing 2–3 neutrons and energy; nuclear fusion is joining two light nuclei (e.g., hydrogen isotopes) at extreme temperature/pressure to form a heavier nucleus (Helium).
4	State the four key kinematics equations for uniform acceleration in GCSE Physics and explain how to interpret distance–time and velocity–time graphs.	1) v = s / t; 2) a = (v − u) / t; 3) v² − u² = 2as. On a distance–time graph, the gradient equals speed. On a velocity–time graph, the gradient equals acceleration and the area under the graph equals displacement (distance travelled).
5	State Newton's First, Second, and Third Laws of Motion.	First Law: If the resultant force on an object is zero, a stationary object stays stationary and a moving object continues at the same velocity. Second Law: Resultant force is directly proportional to acceleration and inversely proportional to mass: F = ma. Third Law: Whenever two objects interact, they exert equal and opposite forces of the same type on each other.
6	What are the wire colours, potentials, and safety functions inside a standard UK three-pin mains plug (230 V, 50 Hz AC)?	Live wire (Brown): carries alternating potential at 230 V (connected to the fuse). Neutral wire (Blue): completes the circuit and is held at or near 0 V. Earth wire (Green and yellow stripes): at 0 V, connected to the metal casing of the appliance to provide a low-resistance path to earth if the live wire touches the case, blowing the fuse.
7	State the Transformer Equations (Vp/Vs = np/ns and VpIp = VsIs) and distinguish between an alternator (AC) and a dynamo (DC) (Triple Science).	Transformer voltage ratio: Vp / Vs = np / ns. For a 100% efficient transformer: Vp × Ip = Vs × Is. Both alternators and dynamos use electromagnetic induction (generator effect): an alternator uses slip rings and brushes to produce alternating current (AC), whereas a dynamo uses a split-ring commutator to produce direct current (DC).
8	How do alpha decay and beta-minus decay alter the mass number (A) and atomic number (Z) of an unstable nucleus?	In Alpha (α) decay, the nucleus emits ⁴₂He, so mass number decreases by 4 (A − 4) and atomic number decreases by 2 (Z − 2). In Beta-minus (β⁻) decay, a neutron changes into a proton and emits ⁰₋₁e, so mass number stays the same (A) and atomic number increases by 1 (Z + 1).
9	Explain why the National Grid uses step-up and step-down transformers to transmit electrical power across the country.	Step-up transformers increase potential difference to ~400,000 V, which decreases the transmission current (since P = VI). Because power wasted due to heating in the cables is P_loss = I²R, a smaller current vastly reduces energy lost as heat, increasing efficiency. Step-down transformers then reduce p.d. to 230 V for safe domestic use.
10	List the 7 regions of the Electromagnetic Spectrum in order of increasing frequency (decreasing wavelength) and state one use for each.	Radio waves (TV/radio broadcasting) → Microwaves (satellite communications, cooking food) → Infrared (thermal imaging, remote controls, heaters) → Visible light (fibre optic communications, photography) → Ultraviolet (fluorescent lamps, sterilising water) → X-rays (medical bone imaging) → Gamma rays (sterilising medical equipment, radiotherapy for cancer).
11	How does a simple DC electric motor keep rotating continuously in one direction?	Opposite sides of the current-carrying rectangular coil carry current in opposite directions inside a magnetic field, experiencing equal and opposite forces (up on one side, down on the other) that create a turning moment. A split-ring commutator reverses the direction of the current around the coil every half-turn so the coil continues rotating in the same direction.
12	Trace the life cycle of a solar-mass star vs a massive star, and explain how Red-Shift provides evidence for the Big Bang (Triple Science).	Nebula → Protostar → Main Sequence Star (hydrostatic equilibrium). Solar-mass star → Red Giant → White Dwarf → Black Dwarf. Massive star → Red Supergiant → Supernova → Neutron Star or Black Hole. Red-shift: light from distant galaxies is shifted to longer wavelengths, showing galaxies are receding and the universe is expanding from an initial hot, dense state (Big Bang).
13	Explain why a skydiver reaches terminal velocity in terms of resultant forces.	Initially, weight (downwards) is much greater than air resistance (upwards), so there is a large downward resultant force and the skydiver accelerates. As speed increases, air resistance increases until air resistance equals weight. At this point, the resultant force is zero, so acceleration is zero and the skydiver falls at constant terminal velocity.
14	Define radioactive half-life (t₁/₂) and calculate the remaining activity of a 640 Bq sample after 3 half-lives.	Half-life is the average time taken for the number of undecayed radioactive nuclei in a sample (or the count rate/activity) to halve. After 3 half-lives: 640 → 320 → 160 → 80 Bq (or 640 × (½)³ = 80 Bq; net decline ratio is 1/8).
15	Define Stopping Distance, Thinking Distance, and Braking Distance, and list factors that increase each.	Stopping Distance = Thinking Distance + Braking Distance. Thinking distance (distance travelled during driver's reaction time) is increased by alcohol/drugs, tiredness, distractions, and higher speed. Braking distance (distance travelled under braking force) is increased by icy/wet roads, worn tyres/brakes, heavy vehicle mass, and higher speed (since Ek = ½mv², doubling speed quadruples braking distance).
16	Compare Alpha (α), Beta (β⁻), and Gamma (γ) nuclear radiation in terms of nature, charge, range in air, penetrating power, and ionising power.	Alpha (α): Helium nucleus (2p + 2n), +2 charge, ~5 cm range in air, stopped by paper/skin, strongly ionising. Beta (β⁻): Fast-moving electron emitted when a neutron turns into a proton, -1 charge, ~1 m range in air, stopped by ~5 mm aluminium, moderately ionising. Gamma (γ): High-frequency electromagnetic wave, 0 charge, infinite range in air, reduced by thick lead/concrete, weakly ionising.
17	What is Specific Latent Heat (L), what is its equation, and why does temperature remain constant during a change of state?	Specific latent heat is the energy required to change the state of 1 kg of a substance with no change in temperature: E = mL (L_f = latent heat of fusion for solid↔liquid; L_v = latent heat of vaporisation for liquid↔gas). During a state change, energy is used to overcome (or form) intermolecular forces of attraction rather than increasing average kinetic energy (temperature).
18	Distinguish between scalar and vector quantities with 3 examples of each, and state the equation for Weight.	Scalars have magnitude only (mass, speed, distance, energy, time). Vectors have both magnitude and direction (weight/force, velocity, displacement, acceleration, momentum). Weight (N) = Mass (kg) × Gravitational field strength (N/kg): W = mg.
19	State Hooke's Law, define the limit of proportionality, and distinguish between elastic and inelastic deformation.	Hooke's Law: The extension of an elastic object (like a spring) is directly proportional to the force applied, provided the limit of proportionality is not exceeded: F = ke. Elastic deformation means the object returns to its original length when the force is removed; inelastic (plastic) deformation means it remains permanently stretched.
20	Compare the rules for current (I), potential difference (V), and total resistance (R) in series vs parallel circuits.	Series circuit: Current is the same everywhere (I1 = I2); total p.d. is shared across components (Vtotal = V1 + V2); total resistance is the sum (Rtotal = R1 + R2). Parallel circuit: p.d. across each branch is equal to the supply p.d. (V1 = V2); total current splits between branches (Itotal = I1 + I2); adding a resistor in parallel DECREASES total resistance.
21	State the density equation and explain how to measure the density of an irregular solid object (GCSE Required Practical).	Density: ρ = m / V (in kg/m³ or g/cm³). For an irregular solid: 1) Measure its mass (m) using a digital top-pan balance; 2) Fill a Eureka (displacement) can with water up to the spout, submerge the object completely, and collect the displaced water in a measuring cylinder to find the exact volume (V); 3) Calculate ρ = m / V.
22	State the GCSE Physics equations for Kinetic Energy (Ek), Gravitational Potential Energy (Ep), and Elastic Potential Energy (Ee).	Kinetic energy: Ek = ½mv² (m = mass in kg, v = speed in m/s). Gravitational potential energy: Ep = mgh (m = mass in kg, g = gravitational field strength in N/kg, h = height in m). Elastic potential energy: Ee = ½ke² (k = spring constant in N/m, e = extension in m).
23	How does a convex (converging) lens differ from a concave (diverging) lens, and what is the lens magnification formula (Triple Science)?	A convex lens bulges outwards and converges parallel light rays to a principal focus (can form real or virtual images). A concave lens curves inwards and diverges parallel rays so they appear to come from a principal focus (always forms a diminished, upright, virtual image). Magnification = Image height ÷ Object height.
24	Compare transverse and longitudinal waves with examples, and state the Wave Equation and Period Equation.	Transverse waves: oscillations are perpendicular to the direction of energy transfer (all electromagnetic waves, water ripples, S-waves). Longitudinal waves: oscillations are parallel to the direction of energy transfer, forming compressions and rarefactions (sound waves, ultrasound, P-waves). Wave speed: v = fλ; Period: T = 1 / f.
25	Use the particle model of gases to explain why heating a fixed volume of gas increases its pressure, and state Boyle's Law.	Heating a gas increases the average kinetic energy and speed of the gas molecules. They collide with the container walls more frequently and with greater force per collision, producing a greater force per unit area (higher pressure). At constant temperature (Boyle's Law): Pressure × Volume = constant (pV = constant).
26	State the core GCSE Electricity equations linking Charge (Q), Current (I), Time (t), Potential Difference (V), Energy (E), Resistance (R), and Electrical Power (P).	1) Q = I × t (Charge in Coulombs = Current in Amps × Time in seconds); 2) E = Q × V (Energy in Joules = Charge × Potential difference in Volts); 3) V = I × R (Ohm's Law); 4) P = V × I and P = I² × R.
27	What is the Motor Effect, how do you use Fleming's Left-Hand Rule, and what is the equation F = BIl (Higher Tier)?	When a current-carrying wire is placed inside a magnetic field, their magnetic fields interact to exert a force on the wire: F = B × I × l (Force in N = Magnetic flux density in Tesla × Current in Amps × Length of wire in m). Fleming's Left-Hand Rule: Thumb = Force (Motion), First finger = Magnetic Field (N to S), Second finger = Conventional Current (+ to -).
28	Explain why a light ray bends towards the normal when entering a denser medium (refraction) using wavefronts.	When a wave enters an optically denser medium (e.g., air into glass) at an angle, one side of the wavefront enters the glass first and slows down while the other side continues faster in air. This causes the wavefront to pivot and bend towards the normal (wavelength decreases while frequency stays constant).
29	State the equations for Moments, Levers, and Pressure in Solids and Liquids (Triple Science).	Moment of a force: M = F × d (Force in N × perpendicular distance from pivot in m; in equilibrium, total clockwise moment = total anticlockwise moment). Solid pressure: p = F / A (in Pascals, Pa = N/m²). Liquid pressure at depth h: p = hρg.
30	State the equations for Power (P), Work Done (W), and Efficiency.	Power: P = E / t = W / t (in Watts, W = J/s). Work Done: W = F × s (Force in N × distance moved in the direction of force in m). Efficiency = Useful output energy transfer ÷ Total input energy transfer (or Useful power output ÷ Total power input).
31	Describe and explain the current-potential difference (I–V) characteristics of an ohmic resistor, a filament lamp, and a semiconductor diode.	Ohmic resistor (at constant temperature): straight line through the origin (I ∝ V, constant resistance). Filament lamp: S-shaped curve flattening at high V—as current increases, the metal filament gets hotter, metal ions vibrate more, colliding more with electrons and increasing resistance. Diode: current flows in one direction only above ~0.6 V (very high resistance in reverse).
32	How does the resistance of a thermistor and an LDR (Light Dependent Resistor) change with temperature and light intensity?	For an NTC thermistor, as temperature increases, its resistance decreases (used in thermostats). For an LDR, as light intensity increases, its resistance decreases (used in automatic street lights).