The threshold wavelength for photoelectric emission from a material is $5500\,\mathring A$. Photoelectrons will be emitted, when this material is illuminated with monochromatic radiation from a

$A.$ $75\,W$ infra-red lamp

$B.$ $10\,W$ infra-red lamp

$C.$ $75\,W$ ultra-violet lamp

$D.$ $10\,W$ ultra-violet lamp

Choose the correct answer from the options given below :

In a photoelectric effect experiment a light of frequency $1.5$ times the threshold frequency is made to fall on the surface of photosensitive material. Now if the frequency is halved and intensity is doubled, the number of photo electrons emitted will be:

In a photoemissive cell with executing wavelength $\lambda $, the fastest electron has speed $v.$ If the exciting wavelength is changed to $\frac{{3\lambda }}{4}$, the speed of the fastest emitted electron will be

An AIR station is broadcasting the waves of wavelength $300$ metres. If the radiating power of the transmitter is $10 kW$, then the number of photons radiated per second is

In photoelectric effect if the intensity of light is doubled then maximum kinetic energy of photoelectrons will become

A small object at rest, absorbs a light pulse of power $20\,mW$ and duration $300\,ns$. Assuming speed of light as $3 \times 10^8\,m / s$. the momentum of the object becomes equal to $.........\times 10^{-17} kg\,m / s$