Oxford Cambridge and RSA
Tuesday 17 June 2025 – Morning
A Level Physics A
H556/03 Unified physics
Time allowed: 1 hour 30 minutes
You must have:
* 1 8 8 9 5 1 6 5 9 3 *
• the Data, Formulae and Relationships Booklet
You can use:
• a scientific or graphical calculator
• a ruler (cm/mm)
* H 5 5 6 0 3 *
Please write clearly in black ink. Do not write in the barcodes.
Centre number Candidate number
First name(s)
Last name
INSTRUCTIONS
• Use black ink. You can use an HB pencil, but only for graphs and diagrams.
• Write your answer to each question in the space provided. If you need extra space use
the lined page at the end of this booklet. The question numbers must be clearly shown.
• Answer all the questions.
• Where appropriate, your answers should be supported with working. Marks might be
given for using a correct method, even if your answer is wrong.
INFORMATION
• The total mark for this paper is 70.
• The marks for each question are shown in brackets [ ].
• Quality of extended response will be assessed in questions marked with an asterisk (*).
• This document has 20 pages.
ADVICE
• Read each question carefully before you start your answer.
© OCR 2025 [601/4743/X] OCR is an exempt Charity
DC (ST/JG) 360406/2 Turn over
for more: tyrionpapers.com
, 2
1 The Earth’s aurora is an atmospheric effect visible in the polar regions.
Electrons in the upper atmosphere initially move vertically downwards along one of the Earth’s
magnetic field lines. They are accelerated by an electric field.
These electrons collide with oxygen atoms causing atomic electrons to be excited to higher
energy levels. The atomic electrons then return to lower energy levels, releasing photons of
green light, red light and ultraviolet.
The accelerated electrons then travel horizontally through the atmosphere, before travelling
vertically along a different magnetic field line, and then completing the circuit by travelling
horizontally back to their starting point.
The situation is shown in Fig. 1.1.
Fig. 1.1
electron flow
acceleration
region
20 000 km magnetic
field
aurora
electron flow
detector
not to scale
(a) The accelerated electrons are accelerated by electric fields parallel to the magnetic field lines.
The length of the acceleration region is 20 000 km and the electric field value is 0.2 mV / m. The
electric field can be assumed to be uniform.
(i) Calculate the kinetic energy gained by the electrons as they pass through the electric field, in
joules.
kinetic energy = .........................................................J [3]
© OCR 2025
for more: tyrionpapers.com
, 3
(ii) State and explain the direction of the electric field required to accelerate the electrons
downwards.
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... [2]
(b) A simplified energy level diagram for atomic oxygen is shown below.
energy (eV)
0
–9.4
–11.7
–13.6
not to scale
Determine the wavelength of the green light emitted.
Fully justify your answer.
wavelength = ....................................................... m [4]
© OCR 2025 Turn over
for more: tyrionpapers.com
Tuesday 17 June 2025 – Morning
A Level Physics A
H556/03 Unified physics
Time allowed: 1 hour 30 minutes
You must have:
* 1 8 8 9 5 1 6 5 9 3 *
• the Data, Formulae and Relationships Booklet
You can use:
• a scientific or graphical calculator
• a ruler (cm/mm)
* H 5 5 6 0 3 *
Please write clearly in black ink. Do not write in the barcodes.
Centre number Candidate number
First name(s)
Last name
INSTRUCTIONS
• Use black ink. You can use an HB pencil, but only for graphs and diagrams.
• Write your answer to each question in the space provided. If you need extra space use
the lined page at the end of this booklet. The question numbers must be clearly shown.
• Answer all the questions.
• Where appropriate, your answers should be supported with working. Marks might be
given for using a correct method, even if your answer is wrong.
INFORMATION
• The total mark for this paper is 70.
• The marks for each question are shown in brackets [ ].
• Quality of extended response will be assessed in questions marked with an asterisk (*).
• This document has 20 pages.
ADVICE
• Read each question carefully before you start your answer.
© OCR 2025 [601/4743/X] OCR is an exempt Charity
DC (ST/JG) 360406/2 Turn over
for more: tyrionpapers.com
, 2
1 The Earth’s aurora is an atmospheric effect visible in the polar regions.
Electrons in the upper atmosphere initially move vertically downwards along one of the Earth’s
magnetic field lines. They are accelerated by an electric field.
These electrons collide with oxygen atoms causing atomic electrons to be excited to higher
energy levels. The atomic electrons then return to lower energy levels, releasing photons of
green light, red light and ultraviolet.
The accelerated electrons then travel horizontally through the atmosphere, before travelling
vertically along a different magnetic field line, and then completing the circuit by travelling
horizontally back to their starting point.
The situation is shown in Fig. 1.1.
Fig. 1.1
electron flow
acceleration
region
20 000 km magnetic
field
aurora
electron flow
detector
not to scale
(a) The accelerated electrons are accelerated by electric fields parallel to the magnetic field lines.
The length of the acceleration region is 20 000 km and the electric field value is 0.2 mV / m. The
electric field can be assumed to be uniform.
(i) Calculate the kinetic energy gained by the electrons as they pass through the electric field, in
joules.
kinetic energy = .........................................................J [3]
© OCR 2025
for more: tyrionpapers.com
, 3
(ii) State and explain the direction of the electric field required to accelerate the electrons
downwards.
..........................................................................................................................................................
..........................................................................................................................................................
..........................................................................................................................................................
..................................................................................................................................................... [2]
(b) A simplified energy level diagram for atomic oxygen is shown below.
energy (eV)
0
–9.4
–11.7
–13.6
not to scale
Determine the wavelength of the green light emitted.
Fully justify your answer.
wavelength = ....................................................... m [4]
© OCR 2025 Turn over
for more: tyrionpapers.com
