Procedure:

1. Insert the red filter (635 nm), set the light intensity switch to strong light, voltage direction switch to ‘-’, and display mode to current display.
2. Set the de-accelerating voltage to 0V and set the current multiplier to X0.001. Gradually increase the de-accelerating voltage until the photo current reaches zero. Record this stopping potential (Vs) for 635 nm. Repeat the procedure for different wavelengths and distances (e.g., 40 cm and 30 cm).

Calculation:

From the graph of Vs versus ν: h = e × slope of the graph

Substitute the values of ΔVs and Δν from the graph to calculate h. The standard value of h is 6.62 × 10⁻³⁴ J·s. The intercept at ν = 0 provides the work function ϕ.

Result:

1. The value of Planck’s constant h is found to be … J·s.
2. The work function ϕ is … V.