Photoelectric Effect

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LEVELJEE Main

Photoelectric effect supports quantum nature of light because

* Multiple Correct Options

(A)

there is a minimum frequency of light below which no photoelectrons are emitted

(B)

the maximum kinetic energy of photoelectrons depends only on the frequency of light and not on its intensity

(C)

even when the metal surface is faintly illuminated, the photoelectrons leave the surface immediately

(D)

electric charge of the photoelectrons is quantized

JEE Main 2004

LEVELJEE Main

The figure shows the variation of photocurrent with anode potential for a photosensitive surface for three different radiations. Let $I_{a}, I_{b}$ and $I_{c}$ be the intensities and $f_{a}, f_{b}$ and $f_{c}$ be the frequencies for the curves $a, b$ and $c$ respectively. Then :

(A)

f_{a} = f_{b}

and

I_{a} < I_{b}

(B)

f_{a} = f_{c}

and

I_{a} = I_{c}

(C)

f_{a} = f_{b}

and

I_{a} = I_{b}

(D)

f_{b} = f_{c}

and

I_{b} = I_{c}

JEE Advanced 1989

LEVELJEE Advanced

A beam of light has three wavelengths $4144 \overset{˚}{A}$ , $4972 \overset{˚}{A}$ and $6216 \overset{˚}{A}$ with a total intensity of $3.6 \times 1 0^{- 3} W m^{- 2}$ equally distributed amongst the three wavelengths. The beam falls normally on an area $1.0 cm^{2}$ of a clean metallic surface of work function $2.3 eV$ . Assume that there is no loss of light by reflection and that each energetically capable photon ejects one electron. Calculate the number of photoelectrons liberated in two seconds.

JEE Advanced 1991

LEVELJEE Advanced

A monochromatic point source $S$ radiating wavelength $6000 \overset{˚}{A}$ , with power $2 W$ , an aperture $A$ of diameter $0.1 m$ and a large screen $S C$ are placed as shown in figure. A photoemissive detector $D$ of surface area $0.5 cm^{2}$ is placed at the centre of the screen. The efficiency of the detector for the photoelectron generation per incident photon is $0.9$ . (a) Calculate the photon flux at (per unit area per unit time) the centre of the screen and the photocurrent in the detector. (b) If the concave lens $L$ of focal length $0.6 m$ is inserted in the aperture as shown, find the new values of photon flux and photocurrent. Assume a uniform average transmission of $80%$ from the lens. (c) If the work function of the photoemissive surface is $1 eV$ , calculate the values of the stopping potential in the two cases (without and with the lens in the aperture).

JEE Advanced 2017

LEVELJEE Advanced

A photoelectric material having work-function $ϕ_{0}$ is illuminated with light of wavelength $λ (λ < \frac{h c}{ϕ _{0}})$ . The fastest photoelectron has a de-Broglie wavelength $λ_{d}$ . A change in wavelength of the incident light by $Δ λ$ results in a change $Δ λ_{d}$ in $λ_{d}$ . Then, the ratio $\frac{Δ λ _{d}}{Δ λ}$ is proportional to

(A)

\frac{λ _{d}^{2}}{λ ^{2}}

(B)

\frac{λ _{d}}{λ}

(C)

\frac{λ _{d}^{3}}{λ}

(D)

\frac{λ _{d}^{3}}{λ ^{2}}

JEE Advanced 2006

LEVELJEE Advanced

The graph between $1/ λ$ and stopping potential ( $V$ ) of three metals having work functions $ϕ_{1}, ϕ_{2}$ and $ϕ_{3}$ in an experiment of photoelectric effect is plotted as shown in the figure. Which of the following statement(s) is/are correct ? (Here, $λ$ is the wavelength of the incident ray).

* Multiple Correct Options

(A)

Ratio of work functions

ϕ_{1} : ϕ_{2} : ϕ_{3} = 1 : 2 : 4

(B)

Ratio of work functions

ϕ_{1} : ϕ_{2} : ϕ_{3} = 4 : 2 : 1

(C)

tan θ

is directly proportional to

h c / e

, where

h

is Planck's constant and

c

is the speed of light

(D)

The violet colour light can eject photoelectrons from metals 2 and 3

JEE Advanced 1995

LEVELJEE Advanced

In a photoelectric effect set-up a point of light of power $3.2 \times 1 0^{- 3}$ W emits monoenergetic photons of energy $5.0$ eV. The source is located at a distance of $0.8$ m from the centre of a stationary metallic sphere of work function $3.0$ eV and of radius $8.0 \times 1 0^{- 3}$ m. The efficiency of photoelectrons emission is one for every $1 0^{6}$ incident photons. Assume that the sphere is isolated and initially neutral and that photoelectrons are instantly swept away after emission. (a) Calculate the number of photoelectrons emitted per second. (b) Find the ratio of the wavelength of incident light to the de-Broglie wavelength of the fastest photoelectrons emitted. (c) It is observed that the photoelectrons emission stops at a certain time $t$ after the light source is switched on why ? (d) Evaluate the time $t$ .

JEE Advanced 2004

LEVELJEE Advanced

Wavelengths belonging to Balmer series lying in the range of $450 nm$ to $750 nm$ were used to eject photoelectrons from a metal surface whose work function is $2.0 eV$ . Find (in eV) the maximum kinetic energy of the emitted photoelectrons. (Take $h c = 1242 eV nm$ .)

LEVELJEE Advanced

Ultraviolet light of wavelengths $800 \overset{˚}{A}$ and $700 \overset{˚}{A}$ when allowed to fall on hydrogen atoms in their ground state is found to liberate electrons with kinetic energy $1.8 eV$ and $4.0 eV$ respectively. Find the value of Planck's constant.

JEE Advanced 2011

LEVELJEE Advanced

A silver sphere of radius 1 cm and work function 4.7 eV is suspended from an insulating thread in free-space. It is under continuous illumination of 200 nm wavelength light. As photoelectrons are emitted, the sphere gets charged and acquires a potential. The maximum number of photoelectrons emitted from the sphere is $A \times 1 0^{Z}$ (where $1 < A < 10$ ). The value of $Z$ is

JEE Advanced 2014

LEVELJEE Main

A metal surface is illuminated by light of two different wavelengths $248 nm$ and $310 nm$ . The maximum speeds of the photoelectrons corresponding to these wavelengths are $u_{1}$ and $u_{2}$ , respectively. If the ratio $u_{1} : u_{2} = 2 : 1$ and $h c = 1240 e V nm$ , the work function of the metal is nearly

Electrons in hydrogen-like atom ( $Z = 3$ ) make transitions from the fifth to the fourth orbit and from the fourth to the third orbit. The resulting radiations are incident normally on a metal plate and eject photoelectrons. The stopping potential for the photoelectrons ejected by the shorter wavelength is $3.95 V$ . Calculate the work function of the metal, and the stopping potential for the photoelectrons ejected by the longer wavelength (Rydberg's constant $= 1.094 \times 1 0^{7} m^{- 1}$ )

JEE Advanced 2002

LEVELJEE Advanced

Two metallic plates $A$ and $B$ each of area $5 \times 1 0^{- 4} m^{2}$ , are placed parallel to each other at separation of $1 cm$ . Plate $B$ carries a positive charge of $33.7 \times 1 0^{- 12} C$ . A monochromatic beam of light, with photons of energy $5 eV$ each, starts falling on plate $A$ at $t = 0$ so that $1 0^{16}$ photons fall on it per square metre per second. Assume that one photoelectron is emitted for every $1 0^{6}$ 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 $2 eV$ . Determine (a) the number of photoelectrons emitted up to $t = 10 s$ , (b) the magnitude of the electric field between the plates $A$ and $B$ at $t = 10 s$ and (c) the kinetic energy of the most energetic photoelectrons emitted at $t = 10 s$ when it reaches plate $B$ . Neglect the time taken by the photoelectron to reach plate $B$ . (Take $ε_{0} = 8.85 \times 1 0^{- 12} C^{2} / N-m^{2}$ ).

JEE Advanced 2013

LEVELBoard

The work functions of silver and sodium are $4.6$ and $2.3 eV$ , respectively. The ratio of the slope of the stopping potential versus frequency plot for silver to that of sodium is

JEE Advanced 2018

LEVELJEE Advanced

In a photoelectric experiment, a parallel beam of monochromatic light with power of $200 W$ is incident on a perfectly absorbing cathode of work function $6.25 eV$ . The frequency of light is just above the threshold frequency, so that the photoelectrons are emitted with negligible kinetic energy. Assume that the photoelectron emission efficiency is $100%$ . A potential difference of $500 V$ is applied between the cathode and the anode. All the emitted electrons are incident normally on the anode and are absorbed. The anode experiences a force $F = n \times 1 0^{- 4} N$ due to the impact of the electrons. The value of $n$ is ........... . (Take mass of the electron, $m_{e} = 9 \times 1 0^{- 31} kg$ and $1 eV = 1.6 \times 1 0^{- 19} J$ )

LEVELJEE Main

The work function of a substance is $4.0 eV$ . The longest wavelength of light that can cause photoelectron emission from this substance is approximately

(A)

540 nm

(B)

400 nm

(C)

310 nm

(D)

220 nm

JEE Advanced 2016

LEVELJEE Main

In a historical experiment to determine Planck's constant, a metal surface was irradiated with light of different wavelengths. The emitted photoelectron energies were measured by applying a stopping potential. The relevant data for the wavelength ( $λ$ ) of incident light and the corresponding stopping potential ( $V_{0}$ ) are given below: \begin{array}{cc} \hline \lambda \text{ (}\mu\text{m)} & V_0 \text{ (Volt)} \\ \hline 0.3 & 2.0 \\ 0.4 & 1.0 \\ 0.5 & 0.4 \\ \hline \end{array} Given that $c = 3 \times 1 0^{8} ms^{- 1}$ and $e = 1.6 \times 1 0^{- 19} C$ , Planck's constant (in units of J-s) found from such an experiment is

(A)

6.0 \times 1 0^{- 34}

(B)

6.4 \times 1 0^{- 34}

(C)

6.6 \times 1 0^{- 34}

(D)

6.8 \times 1 0^{- 34}

LEVELJEE Main

The maximum kinetic energy of photoelectrons emitted from a surface when photons of energy 6 eV fall on it is 4 eV. The stopping potential in volt is

The threshold wavelength for photoelectric emission from a material is $5200 \overset{˚}{A}$ . Photoelectrons will be emitted when this material is illuminated with monochromatic radiation from a

* Multiple Correct Options

50 W ultraviolet lamp

(D)

1 W ultraviolet lamp

LEVELJEE Main

When a beam of $10.6 eV$ photons of intensity $2.0 W/m^{2}$ falls on a platinum surface of area $1.0 \times 1 0^{- 4} m^{2}$ and work function $5.6 eV$ . $0.53%$ of the incident photons eject photoelectrons. Find the number of photoelectrons emitted per second and their minimum and maximum energies (in eV). Take $1 eV = 1.6 \times 1 0^{- 19} J$ .

LEVELBoard

The maximum kinetic energy of electrons emitted in the photoelectric effect is linearly dependent on the ......... of the incident radiation.

JEE Main 2009

LEVELJEE Advanced

Photoelectric effect experiments are performed using three different metal plates $p, q$ and $r$ having work functions $ϕ_{p} = 2.0$ eV, $ϕ_{q} = 2.5$ eV and $ϕ_{r} = 3.0$ eV, respectively. A light beam containing wavelengths of 550 nm, 450 nm and 350 nm with equal intensities illuminates each of the plates. The correct $I - V$ graph for the experiment is

In a photoelectric experiment set-up, photons of energy $5 eV$ falls on the cathode having work function $3 eV$ . (a) If the saturation current is $i_{A} = 4 μ A$ for intensity $1 0^{- 5} W / m^{2}$ , then plot a graph between anode potential and current. (b) Also, draw a graph for intensity of incident radiation $2 \times 1 0^{- 5} W / m^{2}$ .

JEE Advanced 2015

LEVELJEE Main

For photo-electric effect with incident photon wavelength $λ$ , the stopping potential is $V_{0}$ . Identify the correct variation(s) of $V_{0}$ with $λ$ and $\frac{1}{λ}$ .

* Multiple Correct Options

When a monochromatic point source of light is at a distance of 0.2 m from a photoelectric cell, the cut-off voltage and the saturation current are respectively 0.6 V and 18.0 mA. If the same source is placed 0.6 m away from the photoelectric cell, then

* Multiple Correct Options

(A)

the stopping potential will be 0.2 V

(B)

the stopping potential will be 0.6 V

(C)

the saturation current will be 6.0 mA

(D)

the saturation current will be 2.0 mA

Photoelectric effect supports quantum nature of light because

.math-text-wrapper .katex { font-size: 1.05em !important; } .math-text-wrapper .katex-display { margin: 1rem 0 !important; } The work function of a substance is 4.0 eV. The longest wavelength of light that can cause photoelectron emission from this substance is approximately

The maximum kinetic energy of photoelectrons emitted from a surface when photons of energy 6 eV fall on it is 4 eV. The stopping potential in volt is

The maximum kinetic energy of electrons emitted in the photoelectric effect is linearly dependent on the ......... of the incident radiation.

.math-text-wrapper .katex { font-size: 1.05em !important; } .math-text-wrapper .katex-display { margin: 1rem 0 !important; } For photo-electric effect with incident photon wavelength λ, the stopping potential is V0​. Identify the correct variation(s) of V0​ with λ and λ1​.

When a monochromatic point source of light is at a distance of 0.2 m from a photoelectric cell, the cut-off voltage and the saturation current are respectively 0.6 V and 18.0 mA. If the same source is placed 0.6 m away from the photoelectric cell, then

The work function of a substance is $4.0 eV$ . The longest wavelength of light that can cause photoelectron emission from this substance is approximately

For photo-electric effect with incident photon wavelength $λ$ , the stopping potential is $V_{0}$ . Identify the correct variation(s) of $V_{0}$ with $λ$ and $\frac{1}{λ}$ .