Here,
E1 = 2.5eV,
E2 = 2eV,
E3 = 3eV
E = \(\frac{hc}{\lambda}\)
= \(\frac{6.6\times10^{-34}\times 3\times 3 \times 10^8}{600\times 10^{-9}\times 1.6\times 10^{-19}}\) eV
= 2.06 eV
Here,
2.06 eV< E1 and E3
So,
D1 and D3 cannot detect the radiation of wavelength 600 nm.
But, Since,
2.06 eV> E2
Therefore,
D2 can detect the wavelength of 600 nm.