(A) Given: Power of source $P = 1 \,W$, distance $d = 1 \,m$, radius of exposed area $r = 1 \,Å = 10^{-10} \,m$, work function $\phi = 5 \,eV = 5 \tim

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(A) Given: Power of source $P = 1 \,W$, distance $d = 1 \,m$, radius of exposed area $r = 1 \,Å = 10^{-10} \,m$, work function $\phi = 5 \,eV = 5 \times 1.6 \times 10^{-19} \,J$.Intensity $I$ at distance $d$ is $I = \frac{P}{4 \pi d^2} = \frac{1}{4 \pi (1)^2} = \frac{1}{4 \pi} \,W/m^2$.Power absorbed by the circular area $A = \pi r^2$ is $P_{abs} = I \times A = \frac{1}{4 \pi} \times \pi (10^{-10})^2 = \frac{10^{-20}}{4} \,W$.The time $t$ required to accumulate energy equal to the work function is $t = \frac{\phi}{P_{abs}}$.Substituting the values: $t = \frac{5 \times 1.6 \times 10^{-19}}{10^{-20} / 4} = \frac{8 \times 10^{-19}}{0.25 \times 10^{-20}} = 320 \,s$.

Class 12 Physics Dual Nature of Radiation and matter Einstein's Photoelectric Equation and Energy Quantum of Radiation

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$A$ cobalt $(Co)$ plate is placed at a distance of $1 \,m$ from a point source of power $1 \,W$. Assume a circular area of the plate of radius $r = 1 \,Å$ is exposed to the radiation and ejects photoelectrons. The light energy is considered to be spread uniformly and the work function of cobalt is $5 \,eV$. The minimum time the target should be exposed to the light source to eject a photoelectron (assuming no reflection losses) is: (in $\,s$)

TS EAMCET 2019 All TS EAMCET

A
$320$
B
$450$
C
$860$
D
$100$

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Dual Nature of Radiation and matter

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Einstein's Photoelectric Equation and Energy Quantum of Radiation

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When photons of wavelength $\lambda_1$ are incident on an isolated sphere,the corresponding stopping potential is found to be $V$. When photons of wavelength $\lambda_2$ are used,the corresponding stopping potential is thrice that of the above value. If light of wavelength $\lambda_3$ is used,then find the stopping potential for this case.

DifficultJEE MAIN 2016

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When the energy of the incident radiation is increased by $20\%$,the kinetic energy of the photoelectrons emitted from a metal surface increases from $0.5\, eV$ to $0.8\, eV$. The work function of the metal is ............. $eV$.

MediumAIPMT 2014

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The longest wavelength of light that can initiate the photoelectric effect in a metal with a work function of $9 \ eV$ is:

EasyAP EAMCET 2024

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When a metal surface is illuminated by light of wavelength $\lambda$,the stopping potential is $8 \ V$. When the same surface is illuminated by light of wavelength $3 \lambda$,the stopping potential is $2 \ V$. The threshold wavelength for this surface is:

DifficultJEE MAIN 2024

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In a photoelectric cell,the wavelength of incident light is changed from $4000 \, \mathring{A}$ to $3600 \, \mathring{A}$. The change in stopping potential will be ............. $V$.

Medium

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When the energy of the incident radiation is increased by $20\%$,the kinetic energy of the photoelectrons emitted from a metal surface increases from $0.5\, eV$ to $0.8\, eV$. The work function of the metal is ............. $eV$.

The longest wavelength of light that can initiate the photoelectric effect in a metal with a work function of $9 \ eV$ is:

When a metal surface is illuminated by light of wavelength $\lambda$,the stopping potential is $8 \ V$. When the same surface is illuminated by light of wavelength $3 \lambda$,the stopping potential is $2 \ V$. The threshold wavelength for this surface is:

In a photoelectric cell,the wavelength of incident light is changed from $4000 \, \mathring{A}$ to $3600 \, \mathring{A}$. The change in stopping potential will be ............. $V$.

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