Physics · Class 12

Photoelectric collecting curves

A retarding collector removes low-energy electrons first, reaching zero current at the stopping potential. An accelerating collector collects the available electrons, producing saturation. Intensity and frequency move different parts of the curve.

Open the interactive experiment →

Photoelectric collecting curves

தடுக்குமின்னழுத்தம் அதிகரிக்கும்போது ஒளிமின்னோட்டம் குறையும். நிறுத்தும் மின்னழுத்தத்தில் அது பூஜ்யமாகும்.

Key notes, relationships and model limits

Key relationship

V≤−Vs: I=0; −Vs<V<0: I=Is(1+V/Vs); V≥0: I=Is.

Remember

Common trap

The straight retarding branch is a stated illustrative distribution, not a universal experimental shape.

Model limits

Illustrative uniform kinetic-energy distribution gives a linear retarding branch. Saturation scales with intensity; actual photoelectric curves depend on geometry and electron-energy distribution.

What you will learn

Read stopping and saturation from a collecting curve.

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

At1000 THz,φ2 eV gives Vs≈2.136 V; relative intensity3 gives a6 μA saturation in this calibration.

Why this matters

The model connects photoelectric collecting curves with an observable reading. Check the equation and assumptions before applying it.

Before you start

SI units · algebra · graph reading

Check your understanding

Increasing intensity at fixed frequency mainly changes?

Stopping potential
Saturation current
Work function

Read the explanation

More emitted electrons increase saturation; their maximum energy is unchanged.

Course connection: Class XII Chapter 11. Consult the roadmap for CBSE, NEET, JEE Main and Advanced scope.