A-Level A-Level Physics 2 — Questions and Answers
Question 1: What is the strong nuclear force?
- The force of gravity between protons
- The short-range force that holds protons and neutrons together in the nucleus, overcoming electrostatic repulsion between protons (Correct answer)
- The force between electrons
- The force responsible for beta decay
Correct answer: The short-range force that holds protons and neutrons together in the nucleus, overcoming electrostatic repulsion between protons
The strong nuclear force (strong interaction) acts between quarks and holds nucleons (protons and neutrons) together in the nucleus. It is very short-range (< ~3 fm) but extremely powerful, overcoming the electrostatic repulsion between protons.
Question 2: What is the difference between alpha, beta, and gamma radiation?
- They all have the same penetrating power
- Alpha (α) is a helium nucleus (stopped by paper); beta (β) is an electron (stopped by aluminium); gamma (γ) is a high-energy EM wave (reduced by thick lead/concrete) (Correct answer)
- Gamma is stopped by paper
- Beta radiation is the most ionising
Correct answer: Alpha (α) is a helium nucleus (stopped by paper); beta (β) is an electron (stopped by aluminium); gamma (γ) is a high-energy EM wave (reduced by thick lead/concrete)
Alpha particles (⁴₂He) are heavily ionising but have low penetration (stopped by paper or a few cm of air). Beta particles (electrons) have medium penetration (stopped by aluminium). Gamma rays are EM radiation, deeply penetrating, reduced by dense materials.
Question 3: What is the Bohr model of the hydrogen atom?
- Electrons exist in a probability cloud around the nucleus
- Electrons orbit in fixed energy levels; when they transition between levels, they emit or absorb photons of specific frequencies (Correct answer)
- The nucleus contains both protons and electrons
- Electrons are found randomly throughout the atom
Correct answer: Electrons orbit in fixed energy levels; when they transition between levels, they emit or absorb photons of specific frequencies
Bohr's model (1913) proposed electrons occupy fixed circular orbits (energy levels). When an electron drops to a lower level, it emits a photon with energy E = hf = E₂ − E₁. This explained the discrete line spectrum of hydrogen.
Question 4: What is Faraday's Law of Electromagnetic Induction?
- Like magnetic poles repel each other
- The induced EMF in a circuit is proportional to the rate of change of magnetic flux linkage through the circuit (Correct answer)
- Current only flows in one direction
- Magnetic field strength is inversely proportional to distance
Correct answer: The induced EMF in a circuit is proportional to the rate of change of magnetic flux linkage through the circuit
Faraday's Law: EMF = −dΦ/dt (the negative sign comes from Lenz's Law). The induced EMF (and hence current) is proportional to how quickly the magnetic flux through a circuit changes. This is the basis of generators and transformers.
Question 5: What is the principle of superposition of waves?
- Waves cannot pass through each other
- When two waves meet at a point, the resultant displacement is the algebraic sum of the individual displacements (Correct answer)
- Waves always cancel each other out
- Superposition only applies to light waves
Correct answer: When two waves meet at a point, the resultant displacement is the algebraic sum of the individual displacements
The principle of superposition states that when two or more waves overlap, the total displacement at any point is the vector (algebraic) sum of individual displacements. This produces constructive interference (crests align) or destructive interference (crest meets trough).
Question 6: What is the relationship between energy and mass in Einstein's special relativity?
- E = mc
- E = mc² (Correct answer)
- E = mv²
- E = m/c²
Correct answer: E = mc²
Einstein's famous equation E = mc² shows that mass and energy are equivalent and interconvertible. A small mass corresponds to an enormous amount of energy (c ≈ 3 × 10⁸ m/s, so c² ≈ 9 × 10¹⁶). This underpins nuclear energy and particle physics.
A-Level A-Level Physics 2
What is the strong nuclear force?