For a metal of work function 6.6 eV, which of the following wavelengths of incident radiation does not give rise to the photoelectric effect ?
(Take Planck's constant as \(6.6 \times 10^{-34} J s\) )

(C) 200 nm
The threshold wavelength \(\lambda_0\) is given by \(\lambda_0=\frac{h c}{\Phi}\).
Substituting the given values:
\(\lambda_0=\frac{6.6 \times 10^{-34} \times 3 \times 10^8}{6.6 \times 1.6 \times 10^{-19}}\)
\(\lambda_0=\frac{3}{1.6} \times 10^{-7} m\)
\(\lambda_0=1.875 \times 10^{-7} m=187.5 nm\)
For the photoelectric effect to take place, the wavelength of incident radiation must be less than or equal to the threshold wavelength ( \(\lambda \leq \lambda_0\) ).
Among the given options, 200 nm is greater than 187.5 nm .
Thus, radiation of wavelength 200 nm will not give rise to the photoelectric effect.