A-Level H2 Physics 2 — Questions and Answers
Question 1: What is the photoelectric effect?
- Emission of photons by excited atoms
- Emission of electrons from a metal surface when light of sufficient frequency is incident on it (Correct answer)
- The bending of light around obstacles
- The scattering of X-rays by electrons
Correct answer: Emission of electrons from a metal surface when light of sufficient frequency is incident on it
The photoelectric effect is the emission of electrons from a metal surface when light above the threshold frequency is incident on it — evidence for the particle nature of light (photons).
Question 2: What is the de Broglie wavelength of a particle?
- λ = hf
- λ = h/mv (Correct answer)
- λ = mc²/h
- λ = hv/c
Correct answer: λ = h/mv
The de Broglie wavelength: λ = h/p = h/mv, where h is Planck's constant, m is mass, and v is velocity. This shows matter has wave-like properties.
Question 3: In a transformer, the primary coil has 200 turns and the secondary has 50 turns. If the input is 240V, what is the output?
- 60V (Correct answer)
- 960V
- 120V
- 48V
Correct answer: 60V
Vs/Vp = Ns/Np → Vs = 240 × (50/200) = 240 × 0.25 = 60V. This is a step-down transformer.
Question 4: What does the area under a velocity-time graph represent?
- Acceleration
- Force
- Displacement (Correct answer)
- Power
Correct answer: Displacement
The area under a velocity-time graph represents the displacement of the object. Area above the time axis is positive displacement; area below is negative.
Question 5: What is the equation for the energy of a photon?
- E = mv²
- E = hf (Correct answer)
- E = qV
- E = ½hf
Correct answer: E = hf
The energy of a photon is E = hf, where h is Planck's constant (6.63 × 10⁻³⁴ J s) and f is the frequency of the electromagnetic radiation.
Question 6: What happens to the resistance of a semiconductor as temperature increases?
- Resistance increases
- Resistance remains constant
- Resistance decreases (Correct answer)
- Resistance first increases then decreases
Correct answer: Resistance decreases
In semiconductors, increasing temperature provides energy to free more charge carriers (electrons and holes), increasing conductivity and decreasing resistance — opposite to metals.
A-Level H2 Physics 2
What is the photoelectric effect?