If the two metals $A$ and $B$ are exposed to radiation of wavelength $350\,nm$. The work functions of metals $A$ and $B$ are $4.8\,eV$ and $2.2\,eV$. Then choose the correct option

There are two sources of light, each emitting with a power of $100 \,W.$ One emits $X-$ rays of wavelength $1\, nm$ and the other visible light at $500\, nm$. Find the ratio of number of photons of $X-$ rays to the photons of visible light of the given wavelength ? 

The time taken by a photoelectron to come Out after the photon strikes is approximately

A $100\,watt$ light source is emitting radiations of wavelength $5000\,\mathop A\limits^o $. The rate of emission of photons is of the order of

The energy equivalent to $1\,mg$ of matter in $MeV$ is

The light of two different frequencies whose photons have energies $3.8 \,eV$ and $1.4 \,eV$ respectively, illuminate a metallic surface whose work function is $0.6 \,eV$ successively. The ratio of maximum speeds of emitted electrons for the two frequencies respectivly will be