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Waves and quantum behaviour

From Paper 1: Fundamentals of physics
131 mark
A path difference of λ/2 gives a phase difference of:
From Paper 1: Fundamentals of physics
141 mark
What is the energy of a photon of frequency 5.0 × 10¹⁴ Hz?
From Paper 1: Fundamentals of physics
151 mark
An electron is accelerated through 100 V. Its kinetic energy gain is:
From Paper 1: Fundamentals of physics
161 mark
Light of 650 nm passes through slits 0.50 mm apart onto a screen 2.0 m away. The fringe spacing is:
From Paper 1: Fundamentals of physics
34(a)4 marks
In a two-slit experiment, slits 0.40 mm apart give fringes 2.4 mm apart on a screen 1.5 m away. Calculate the wavelength and use phasors to explain why there is a bright fringe where the path difference is a whole number of wavelengths.
From Paper 1: Fundamentals of physics
34(b)4 marks
Electrons accelerated through 5.0 kV pass through a graphite film. Calculate their de Broglie wavelength and explain the pattern using the idea that quanta 'explore all paths'.
From Paper 1: Fundamentals of physics
34(c)3 marks
A red LED (650 nm) just starts to emit light at 1.9 V. Use this to estimate the Planck constant.
From Paper 2: Scientific literacy in physics
5(b)3 marks
In a microwave oven, hot spots (antinodes) are 6.1 cm apart. Calculate the frequency of the microwaves.

Advance Notice article (written for this paper): Seeing inside the body with antimatter

(1) Positron emission tomography (PET) builds a three-dimensional map of where a radioactive tracer collects in the body. The most common tracer is a sugar labelled with fluorine-18, which decays by β⁺ emission with a half-life of 110 minutes. (2) Because fluorine-18 decays so quickly, it is made in a cyclotron close to the hospital. A typical dose leaves the cyclotron at 08:00 with an activity of 2.0 GBq and is injected about two hours later. (3) Each positron travels about a millimetre through tissue before it meets an electron. The pair annihilates, producing two gamma photons, each of energy 511 keV, which travel in almost exactly opposite directions. (4) A ring of detectors surrounds the patient. When two detectors on opposite sides register photons within a few nanoseconds of each other, the annihilation must have happened somewhere on the line joining them. Modern scanners also measure the tiny difference in arrival times to locate the event along that line. (5) A scan typically collects about 4 × 10⁸ such coincidences in 20 minutes. Like all counting experiments, the image is noisy: the uncertainty in N counts is about √N. (6) A PET scan gives the patient an effective dose of about 7 mSv, compared with an average background dose in the UK of 2.7 mSv per year. The commonly used risk estimate is a 5% chance of a fatal cancer per sievert. (7) PET shows what tissues are doing (for example, fast-growing tumours take up more sugar), while X-ray CT shows their structure. Many scanners combine the two.
From Paper 2: Scientific literacy in physics
8(b)4 marks
Explain why the two photons in paragraph 3 travel in opposite directions and each have energy 511 keV, and calculate their wavelength.
From Paper 3: Practical skills in physics
1(a)3 marks
Describe how to find the voltage at which an LED just begins to emit light, and how to make the judgement as reliable as possible.
From Paper 3: Practical skills in physics
1(b)5 marks
Results:
λ / nm470525590625660
V / V2.6452.3682.1071.9891.884
Figure 1 shows V against 1/λ. Use it to determine the Planck constant.
1.41.61.822.21.622.42.8(1/λ) / 10⁶ m⁻¹V / Vdatabest fit
Figure 1
From Paper 3: Practical skills in physics
4(a)3 marks
Describe how to find the shortest resonant length of an air column closed at one end for a given tuning fork.
From Paper 3: Practical skills in physics
4(b)5 marks
Results:
f / Hz256320384426512
L / m0.3230.2570.2120.1910.157
The model is L = v/(4f) − e, where e is the end correction. Use a suitable graph to find v and e.
Score 0 / 38 · 0 of 13 marked

This paper is written by Plasmo in the style of the OCR A-Level Physics exam. It is not a past paper and is not produced or endorsed by the exam board.

Waves and quantum behaviour Exam Questions: OCR A-Level Physics | Plasmo