TalentJR apps
A line follower robot uses light sensors that shine light at the floor and measure how much comes back. White reflects a lot (a high reading); black soaks up light (a low reading). The threshold is the cut-off between them — a good choice is halfway between the black and white readings. With two sensors, one on each side of the line, the robot knows where the line is: if the left sensor reads black, the line is under the left sensor.
✓ You passed this lesson’s test.
Below the threshold is black — “black soaks up light, so a low reading means the sensor is over the line”
Use it for: Building or programming a line follower robot, robotics competitions and science lessons on light.
Check: With readings 20 and 80, a halfway threshold is (20 + 80) ÷ 2 = 50 ✓
▶ Watch it animatedWork it out in your head or on paper, type the answer and press Check. Stuck? Press “Show me how”.
Right: 0 · Tried: 0
20 questions. Check each answer, then go to the next one. Get 16 or more right to pass.
🏅 Sign in with Google to earn the 🔦 Line Spotter badge when you pass — and a certificate when you finish all 10 lessons of Part 2 · How robots move and sense. You can still take the test without signing in.
Why does it work? When should you use it? Ask in English, मराठी or हिंदी.
Sign in with Google to ask Free — 20 questions a day.
Prefer a real teacher? TalentJR teachers take live online classes anywhere in India and visit homes in selected cities. Tell us what you need and our team will call you with timings and fees.