Lesson 7 · Detecting Intersections — Knowledge ChecksAnswer key

Which condition detects an intersection (both sensors on the line)?

1. A.left > 0.5 or right > 0.5
2. B.left > 0.5 and right > 0.5✓
3. C.left > 0.5
4. D.not (left > 0.5)

A cross means BOTH sensors are on black at once, so both comparisons must be true — that's and. or would fire during normal following too.

Why is there a time.sleep(0.3) right after the robot turns at the cross?

1. A.To let the motors cool down
2. B.So the robot moves past the cross before the loop checks again — otherwise it re-detects the same cross instantly✓
3. C.To make the turn more accurate
4. D.It is required by arcade()

Right after turning, both sensors are still on the cross. The brief pause lets the robot drive clear so it doesn't detect the same intersection over and over.

During normal line following (not at a cross), which branch of the if/else runs?

1. A.The if branch — it turns around
2. B.The else branch — it does proportional line following✓
3. C.Both branches run
4. D.Neither runs

Only one branch runs. When the sensors differ (not both high), the cross condition is false, so the else branch does normal following.