The Uncertainty Principle

Q. If a photon of intensity $I$ falls on a surface at an angle ${60}^{\circ }$ making with it having absorption coefficient $0.4$, then radiation pressure exerted on the surface is-

1. $\frac{0.4I}{c}$
2. $\frac{1.2I}{c}$
3. $\frac{1.05I}{c}$
4. $\frac{7I}{20c}$

Q. An excited atom gives up its excess energy by emitting a photon of certain characteristic frequency. The average time period that elapses between the excitation of an atom and the time it radiates is $1.0\times {10}^{-8}s$. What is the inherent uncertainty in the frequency of the photon?

1. $8\times {10}^{6}Hz$
2. $8\times {10}^{7}Hz$
3. $8\times {10}^{8}Hz$
4. $8\times {10}^{9}Hz$

Q. A typical atomic nucleus is about $5.0\times {10}^{-15}m$ in radius. Using the uncertainty principle, what should be the lower limit on momentum, that a particle must have if it is to be a part of a nucleus?

1. $1.1\times {10}^{-20}kgm/s$
2. $2.2\times {10}^{-20}kgm/s$
3. $4.4\times {10}^{-20}kgm/s$
4. No lower limit