Electromagnetic radiation is incident on a metal surface. It is observed that there is a minimum frequency of electromagnetic radiation below which emission of electrons does not occur. This observation provides evidence for a particulate nature of electromagnetic radiation. The maximum kinetic energy E_MAX of electrons emitted from a metal surface is determined for different wavelengths λ of the electromagnetic radiation incident on the surface. The variation with 1/λ of E_MAX is shown in [Figure 11.1].

1. (a)State two other observations associated with photoelectric emission that provide evidence for a particulate nature of electromagnetic radiation.[2]
2. (b)(i)Use [Figure 11.1] to determine the threshold frequency f₀.[2]
3. (b)(ii)Use the gradient of the line on [Figure 11.1] to determine a value for the Planck constant h. Explain your working.[4]
4. (c)The electromagnetic radiation is now incident on a metal with a larger work function energy than the metal in (b). On [Figure 11.1], sketch the variation with 1/λ of E_MAX.[2]

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