Key relationship
E=E1m/d²; illustrative R=1 MΩ/[1+√(E/10 lux)].
Physics · Practical apparatus
LDR lamp distance readings
Change distance while holding lamp output fixed. Illuminance falls with distance squared, while the resistance response is nonlinear. Read resistance rather than treating it as a direct light intensity.
Open the interactive experiment →LDR lamp distance readings
விளக்கின் வெளியீடு நிலையாக இருக்கும்போது தொலைவு அதிகரித்தால் ஒளிச்செறிவு குறைந்து LDR மின்தடை அதிகரிக்கும்.
Key notes, relationships and model limits
Practical tip
Change distance while holding lamp output fixed. Illuminance falls with distance squared, while the resistance response is nonlinear. Read resistance rather than treating it as a direct light intensity.
Common trap
A measured resistance-to-lux conversion requires the actual sensor’s calibration.
Model limits
Point-lamp inverse-square approximation, fixed source and dark-room background0. Empirical LDR law is prescribed, not a universal sensor calibration.
What you will learn
Investigate distance-dependent LDR resistance.
Try the experiment
Try both scenarios, change one control, and predict the result before checking the graph and readouts.
Think of it this way
Change one input while keeping the others fixed, as you would in a controlled experiment.
Worked example
100 lux at1 m becomes400 lux at0.5 m in the ideal point-source guide.
Why this matters
The model connects ldr lamp distance readings with an observable reading. Check the equation and assumptions before applying it.
Before you start
SI units · algebra · graph reading
Check your understanding
Doubling lamp distance changes point-source illuminance to?
- Half
- One quarter
- Four times
Read the explanation
Inverse square gives1/2².
Course connection: Virtual apparatus preparation. Check exact board/exam membership in the syllabus sources. Physical practical work remains necessary.