10 GCSE Physics questions about the VR headset, from Foundation to Higher, each with a full worked answer. A VR headset holds a small screen just a few centimetres from your eyes – far too close to focus on by yourself. A convex lens in front of each eye acts like a magnifying glass, making a large, virtual image that looks further away, while the screen refreshes around 90 times a second so movement looks smooth.
Course: Combined Science + Separate Physics (lens questions are Separate Physics only) | Tier: Foundation + Higher | Topics: Waves, Electricity, Energy
📌 KEY DEFINITIONS – learn them word for word
Frequency: the number of waves passing a point each second (for a screen or a vibration, the number of complete cycles each second). Measured in hertz (Hz).
Period: the time taken for one complete wave (or one complete cycle). Period = 1 ÷ frequency.
Focal length (S only): the distance from the lens to the principal focus. A convex lens can form a real or a virtual image; an object closer to the lens than the principal focus gives a virtual, upright, magnified image.
Equations you’ll use
T = 1 ÷ f | E = P t | Q = I t | E = Q V | magnification = image height ÷ object height (S only)
| Quantity | Symbol | Unit |
|---|---|---|
| period | T | seconds (s) |
| frequency | f | hertz (Hz) |
| energy transferred | E | joules (J) |
| power | P | watts (W) |
| time | t | seconds (s) |
| charge flow | Q | coulombs (C) |
| current | I | amperes (A) |
| potential difference | V | volts (V) |
| magnification | – | no unit (heights in the same unit) |
Use FIFA for every answer
- F – Formula: write the equation as it appears on the sheet.
- I – Insert: put in the numbers (convert to standard units first).
- F – Fix: rearrange to make the unknown the subject.
- A – Answer: calculate and always give the unit.
Questions
Q1 (F) A VR headset’s screen has a refresh rate (frequency) of 90 Hz. Calculate the time between one picture and the next, in milliseconds, to 2 significant figures.
Show solution
F: T = 1 ÷ f
I: T = 1 ÷ 90
F: T is already the subject
A: T = 0.0111… s = 11 ms (2 s.f.)
Q2 (F) In a faster mode, a new picture appears every 8.3 ms. Calculate the refresh rate, to 2 significant figures.
Show solution
Convert first: 8.3 ms = 0.0083 s
F: T = 1 ÷ f
I: 0.0083 = 1 ÷ f
F: f = 1 ÷ 0.0083 = 120.5 Hz
A: 120 Hz (2 s.f.)
Q3 (F) The headset has an average power of 8.0 W. Calculate the energy it uses in a 2-hour session, in kJ.
Show solution
Convert first: 2 hours = 2 × 3600 = 7200 s
F: E = P t
I: E = 8.0 × 7200
F: E is already the subject
A: 57 600 J = 57.6 kJ
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Q4 (F) The screen refreshes at 90 Hz. Calculate how many pictures it shows during a 20-minute game.
Show solution
Convert first: 20 minutes = 20 × 60 = 1200 s
Idea: 90 Hz means 90 pictures every second
Calculation: 90 × 1200
A: 108 000 pictures
Q5 (F/H) When fully charged, the headset’s battery can supply a current of 5.0 A for 1.0 hour. (a) Calculate the charge it stores in coulombs. (b) The average current drawn is 2.2 A. Calculate the battery life in hours, to 2 significant figures.
Show solution
Convert first: 1.0 hour = 1.0 × 3600 = 3600 s
(a) F: Q = I t
I: Q = 5.0 × 3600
A: 18 000 C
(b) F: Q = I t
I: 18 000 = 2.2 × t
F: t = 18 000 ÷ 2.2 = 8182 s
A: 8182 ÷ 3600 = 2.3 hours (2 s.f.)
Q6 (F/H) The battery stores 18 000 C at a potential difference of 3.8 V. Calculate the energy stored, in kJ.
Show solution
F: E = Q V
I: E = 18 000 × 3.8
F: E is already the subject
A: 68 400 J = 68.4 kJ
Q7 (F/H · S only) A character on the screen is 1.5 cm tall. Through the lens, the image of the character is 12 cm tall. Calculate the magnification.
Show solution
F: magnification = image height ÷ object height
I: magnification = 12 ÷ 1.5
F: magnification is already the subject
A: 8 (no unit)
Q8 (F/H · S only) The screen is placed 3.5 cm from a convex lens with a focal length of 4.0 cm. Describe the image formed. Give three features. [3 marks]
Show answer
The screen is closer to the lens than the principal focus (3.5 cm < 4.0 cm), so the lens acts as a magnifying glass. The image is:
• virtual – it can’t be projected on a screen; it is where the rays appear to come from (1)
• upright – the same way up as the object (1)
• magnified – bigger than the object, and on the same side of the lens as the screen (1)
Q9 (H · S only) The lens gives a magnification of 8. A menu button appears 20 cm tall in the image. Calculate its real height on the screen, in mm.
Show solution
F: magnification = image height ÷ object height
I: 8 = 20 ÷ object height
F: object height = 20 ÷ 8 = 2.5 cm
A: 25 mm
Q10 (H · S only) Explain how the convex lenses in a VR headset allow the user to see a clear, large image of a screen that is only a few centimetres from their eyes. You may draw a ray diagram as part of your answer. [6 marks]
Show answer
Model answer – marking points:
• The eye cannot focus on an object only a few centimetres away – it would look blurred.
• Each lens is convex (converging): it refracts light so that rays are bent towards the principal axis.
• The screen is placed between the lens and its principal focus (closer than one focal length).
• The rays leaving the lens are diverging; they never meet, but they appear to come from a point further back.
• So the lens forms a virtual, upright, magnified image that is further away from the eye than the screen is.
• Because the image is further away, the eye can focus on it comfortably, and because it is magnified it fills most of the field of view.
Ray diagram: one ray parallel to the axis refracted through the principal focus; one ray straight through the centre of the lens; extend both back with dashed lines to where they meet to find the virtual image.
⚠️ Where students lose marks
- Forgetting to convert milliseconds to seconds before using T = 1 ÷ f (8.3 ms = 0.0083 s).
- Giving magnification a unit, or using image and object heights in different units.
- Saying the image in a VR headset is real – it can’t be put on a screen, so it is virtual. In ray diagrams, virtual rays must be drawn as dashed lines.
- Putting milliamps or hours straight into Q = I t – change mA to A and hours to seconds first.
More devices: all 40 everyday devices · Waves questions · Electricity questions
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