Question

Why does Cesium exhibit the photoelectric effect for red-orange light but Tungsten does not?

What is the ultraviolet catastrophe and why would it suck if it were real?

Answer 1

For a material to exhibit the photoelectric effect, the photon energy must be greater than the work function

For caesium, work function is around 2 eV and for red and orange wavelengths, the photon energy is close or greater than 2 eV

However, tungsten has high work function which is 4.58 eV and the photon energy is much lesser than this, that's why it does not exhibit any photoelectric effect for red / orange.

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In simple words, the divergence of jean-rayleigh law at higher frequencies is called as ultraviolet catastrophe. It basically is a failure of classical physics to predict observed phenomena.