To determine the wavelength of the radiation used to emit photoelectrons from a metal surface with a work function of 1.7 eV and a stopping potential of 10.4 V, we can follow these steps:

Step 1: Understand the Concept
- The **photoelectric effect** explains how light can eject electrons from a metal surface.
- The energy of the incoming photons must overcome the work function of the metal and provide kinetic energy to the emitted electrons.

Step 2: Calculate the Energy of the Photons
- The **stopping potential (V)** gives the maximum kinetic energy (KE) of the emitted electrons:
- KE = e × V
- Here, e (the charge of an electron) = 1.6 × 10⁻¹⁹ C, and V = 10.4 V.
- Thus, KE = 1.6 × 10⁻¹⁹ C × 10.4 V = 1.664 × 10⁻¹⁸ J.
- To convert this energy to electron volts (eV):
- KE = 10.4 eV.
- The total energy of the incoming photon (E) is given by:
- E = Work function + KE = 1.7 eV + 10.4 eV = 12.1 eV.

Step 3: Convert Energy to Wavelength
- Use the equation relating energy and wavelength:
- E = (hc)/λ, where h = Planck’s constant (4.14 × 10⁻¹⁵ eV·s), and c = speed of light (3 × 10⁸ m/s).
- Rearranging gives:
- λ = (hc)/E.
- Substituting the values:
- λ = (4.14 × 10⁻¹⁵ eV·s × 3 × 10⁸ m/s) / 12.1 eV.
- λ ≈ 1.02 × 10⁻⁷ m = 102 nm.

Conclusion
- The wavelength of the radiation used is approximately **102 nm**. This falls in the ultraviolet range, indicating that higher-energy photons are required to overcome the work function and produce photoelectrons.