Q: If h is Planck’s constant is SI system, the momentum of a photon of wavelength 0.01 A° is:

(A) 10^{–2} h

(B) h

(C) 10^{2}

(D) 10^{12}h

**Solution :** $\large \lambda = \frac{h}{p}$

$\large p = \frac{h}{\lambda}$

$\large p = \frac{h}{0.01 \times 10^{-10}}$

p = 10^{12}h