If mean wavelength of light radiated by $100 W$ lamp is $5000 \mathring A$, then number of photons radiated per second are

If a source of power $4\,kW$ produces $10^{20}$ photons/second, the radiation belongs to a part of the spectrum called

A source $S_1$ is producing, $10^{15}$ photons per second of wavelength $5000 \;\mathring A.$ Another source $S_2$ is producing $1.02 \times 10^{15}$ photons per second of wavelength $5100\;\mathring A$. Then, $($ power of $S_2)/$  $($ power of $S_1)$ is equal to

According to photon theory of light which of the following physical quantities associated with a photon do not/does not change as it collides with an electron in vacuum

For photo-electric effect with incident photon wavelength $\lambda$, the stopping potential is $V _0$. Identify the correct variation$(s)$ of $V _0$ with $\lambda$ and $1 / \lambda$. $Image$

A caesium photocell, with a steady potential difference of $60V$ across, is illuminated by a bright point source of light $50 cm$ away. When the same light is placed 1m away the photoelectrons emitted from the cell