New
New
Year 11

Optical sensors for navigation

I can describe and use optical reflective sensors to react to an environment.

New
New
Year 11

Optical sensors for navigation

I can describe and use optical reflective sensors to react to an environment.

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Lesson details

Key learning points

  1. Reflective optical sensors detect surface contrast.
  2. Reflective optical sensors emit infrared light and measure how much is reflected back.
  3. Light coloured surfaces like white reflect more infrared, while dark surfaces like black lines reflect less.

Keywords

  • Environment - the surroundings or conditions something exists in or reacts to

  • Optical - something that relates to light and vision

  • Reflective - something that bounces back light or other waves like sound

Common misconception

The sensor follows the line like a smart camera.

The sensor sends data back to the microcontroller to say whether light or dark is detected. The written code uses this data to decide how the buggy should respond.


To help you plan your year 11 computing lesson on: Optical sensors for navigation, download all teaching resources for free and adapt to suit your pupils' needs...

Engage learners by sharing products that use optical sensors such as a line following robot or a TV remote and IR receiver to physically demonstrate how optical reflective sensors work. Let students interact with the sensor and discuss their ideas for other useful applications of optical sensors.
Teacher tip

Equipment

Raspberry Pi Pico, two optical sensors, jumper wires, previous project materials such as a buggy chassis, Thonny software.

Licence

This content is © Oak National Academy Limited (2025), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

Lesson video

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Prior knowledge starter quiz

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6 Questions

Q1.
What does a sensor do?

draws pictures
stores passwords
Correct answer: detects or measures a physical property
plays music

Q2.
What does an ultrasonic sensor measure?

Correct Answer: distance

Q3.
What does an ultrasonic sensor use to measure distance?

Correct answer: sound waves
light waves
water waves
magnetic fields

Q4.
Which formula is used by ultrasonic sensors to calculate distance?

distance = mass × acceleration
Correct answer: distance = time × speed of sound
distance = force ÷ area
distance = voltage × current

Q5.
Put these steps in order for how an ultrasonic sensor measures distance:

1 - sensor sends out a sound wave
2 - sound wave hits an object
3 - sensor receives the reflected wave
4 - sensor calculates the distance

Q6.
What device receives data from sensors and makes decisions based on that data?

Correct Answer: microcontroller

Assessment exit quiz

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6 Questions

Q1.
What does a reflective optical sensor detect?

sound waves
air temperature
magnetic fields
Correct answer: surface contrast

Q2.
What type of light do reflective optical sensors use?

Correct Answer: infrared, infrared light

Q3.
Match each keyword to its meaning:

Correct Answer:optical,related to light and vision

related to light and vision

Correct Answer:reflective,bounces back light

bounces back light

Correct Answer:environment,the surroundings or conditions

the surroundings or conditions

Correct Answer:microcontroller,receives sensor data and makes decisions

receives sensor data and makes decisions

Q4.
What happens when a reflective optical sensor passes over a white surface?

no light is reflected
the sensor stops working
Correct answer: more infrared is reflected
less infrared is reflected

Q5.
What is the main job of the microcontroller in a line-following robot?

Correct answer: to make decisions based on sensor data
to emit light
to reflect light
to change the environment

Q6.
Put these steps in order for how a reflective optical sensor works:

1 - sensor emits infrared light
2 - light hits a surface
3 - light is reflected back
4 - sensor measures reflected light
5 - data sent to microcontroller
6 - code decides how to respond
7 - robot moves accordingly

Additional material

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