A beam of electromagnetic radiation of intensity $6.4 \times 10^{-5}\; \mathrm{W} / \mathrm{cm}^{2}$ is comprised of wavelength, $\lambda=310 \;\mathrm{nm} .$ It falls normally on a metal (work function $\varphi=2 \;\mathrm{eV}$ ) of surface area of $1\; \mathrm{cm}^{2} .$ If one in $10^{3}$ photons ejects an electron, total number of electrons ejected in $1 \;s$ is $10^{\mathrm{x}}$.then $\mathrm{x}$ is
$\left(\mathrm{hc}=1240\; \mathrm{eV} \mathrm{nm}, 1\; \mathrm{eV}=1.6 \times 10^{-19} \;\mathrm{J}\right)$
A beam of electromagnetic radiation of intensity $6.4 \times 10^{-5}\; \mathrm{W} / \mathrm{cm}^{2}$ is comprised of wavelength, $\lambda=310 \;\mathrm{nm} .$ It falls normally on a metal (work function $\varphi=2 \;\mathrm{eV}$ ) of surface area of $1\; \mathrm{cm}^{2} .$ If one in $10^{3}$ photons ejects an electron, total number of electrons ejected in $1 \;s$ is $10^{\mathrm{x}}$.then $\mathrm{x}$ is
$\left(\mathrm{hc}=1240\; \mathrm{eV} \mathrm{nm}, 1\; \mathrm{eV}=1.6 \times 10^{-19} \;\mathrm{J}\right)$
- [JEE MAIN 2020]
- A
$5$
- B
$8$
- C
$11$
- D
$13$
Similar Questions
A point source is emitting sound waves of intensity $16 \times 10^{-8} \mathrm{Wm}^{-2}$ at the origin. The difference in intensity (magnitude only) at two points located at a distances of $2 \mathrm{~m}$ and $4 \mathrm{~m}$ from the origin respectively will be______ $\times 10^{-8} \mathrm{Wm}^{-2}$
A point source is emitting sound waves of intensity $16 \times 10^{-8} \mathrm{Wm}^{-2}$ at the origin. The difference in intensity (magnitude only) at two points located at a distances of $2 \mathrm{~m}$ and $4 \mathrm{~m}$ from the origin respectively will be______ $\times 10^{-8} \mathrm{Wm}^{-2}$
- [JEE MAIN 2024]
Assertion : The photoelectrons produced by a monochromatic light beam incident on a metal surface, have a spread in their kinetic energies.
Reason : The work function of the metal varies as a function of depth from the surface.
Assertion : The photoelectrons produced by a monochromatic light beam incident on a metal surface, have a spread in their kinetic energies.
Reason : The work function of the metal varies as a function of depth from the surface.
- [AIIMS 2006]
Estimating the following two numbers should be interesting. The first number will tell you why radio engineers do not need to worry much about photons! The second number tells you why our eye can never ‘count photons’, even in barely detectable light.
$(a)$ The number of photons emitted per second by a Medium wave transmitter of $10\; kW$ power, emitting radiowaves of wavelength $500\; m$.
$(b)$ The number of photons entering the pupil of our eye per second corresponding to the minimum intensity of white light that we humans can percetve $(-10^{-10}\; W m ^{-2}$). Take the area of the pupil to be about $0.4 \;cm ^{2}$, and the average frequency of white light to be about $6 \times 10^{14}\; Hz$
Estimating the following two numbers should be interesting. The first number will tell you why radio engineers do not need to worry much about photons! The second number tells you why our eye can never ‘count photons’, even in barely detectable light.
$(a)$ The number of photons emitted per second by a Medium wave transmitter of $10\; kW$ power, emitting radiowaves of wavelength $500\; m$.
$(b)$ The number of photons entering the pupil of our eye per second corresponding to the minimum intensity of white light that we humans can percetve $(-10^{-10}\; W m ^{-2}$). Take the area of the pupil to be about $0.4 \;cm ^{2}$, and the average frequency of white light to be about $6 \times 10^{14}\; Hz$
An electron and a photon have same wavelength of $10^{-9} \,m$. If $E$ is the energy of the photon and $p$ is the momentum of the electron, then the magnitude of $E / p$ (in $SI$ unit) is
An electron and a photon have same wavelength of $10^{-9} \,m$. If $E$ is the energy of the photon and $p$ is the momentum of the electron, then the magnitude of $E / p$ (in $SI$ unit) is
- [KVPY 2016]
Two metallic plates $A$ and $B$, each of area $5 ×10^{-4}m^2$ are placed parallel to each other at a separation of $1\ cm$. Plate $B$ carries a positive charge of $33.7 \,pc$. $A$ monochromatic beam of light, with photons of energy $5\, eV$ each, starts falling on plate $A$ at $t = 0$, so that $10^{16}$ photons fall on it per square meter per second. Assume that one photoelectron is emitted for every $10^{6}$ incident photons. Also assume that all the emitted photoelectrons are collected by plate $B$ and the work function of plate $A$ remains constant at the value $2\, eV$. Electric field between the plates at the end of $10$ seconds is
Two metallic plates $A$ and $B$, each of area $5 ×10^{-4}m^2$ are placed parallel to each other at a separation of $1\ cm$. Plate $B$ carries a positive charge of $33.7 \,pc$. $A$ monochromatic beam of light, with photons of energy $5\, eV$ each, starts falling on plate $A$ at $t = 0$, so that $10^{16}$ photons fall on it per square meter per second. Assume that one photoelectron is emitted for every $10^{6}$ incident photons. Also assume that all the emitted photoelectrons are collected by plate $B$ and the work function of plate $A$ remains constant at the value $2\, eV$. Electric field between the plates at the end of $10$ seconds is