Correct answer is option A

The power of the given laser light is expressed as

$P=\frac{nhc}{\lambda t}$

from which the number of photons per second is given by

$n=P\left(\frac{\lambda t}{hc}\right)=(5\times {10}^2)\times \left[\frac{(660\times {10}^{-9})(60\times {10}^{-3})}{(6.6\times {10}^{-34})(3\times {10}^8)}\right]$

$=100\times {10}^{18}={10}^{20}$

Correct answer is option A

Power, $P=\frac{nhv}{t}$

$\Rightarrow v=\frac{P\times t}{nh}$

$=\frac{4\times {10}^3\times 1}{{10}^{20}\times 6.63\times {10}^{-34}}=6\times {10}^{16}Hz$

Correct answer is option A

Energy of a photon of frequency $v$ is given by $E=hv.$

Also, $E=m{c}^2,m{c}^2=hv$

$\Rightarrow mc=\frac{hv}{C}\Rightarrow p=\frac{hv}{c}$

Correct answer is option A

$I\propto \frac{1}{r^2};\frac{I_1}{I_2}={\left(\frac{r_2}{r_1}\right)}^2=\frac{1}{4}$

$I_2\to 4$ times $I_1$

When intensity becomes 4 times, no. of photoelectrons emitted would increase by $4$ times, since number of electrons emitted per second is directly proportional to intensity.