Dual Nature Of Radiation - Modern Physics - Physics Previous Year Questions

The value of planck's constant, if the slope of the graph of stopping potential versus frequency of incident light is $4 \times 10^{-15} \mathrm{~V}$-s is (given charge of an electron $=1.6 \times 10^{-19} \mathrm{C}$ )

The light emitted in the transition $n=3$ to $n=2$, (where $n$ is the principal quantum number of the state) in hydrogen is called $\mathrm{H}_\alpha$-light. Find the maximum work function that a metal can have, so that $\mathrm{H}_\alpha$-light can emit photoelectrons from it.

The additional energy that should be given to an electron to reduce its de-Broglie wavelength from 1 nm to 0.5 nm is

Consider two black bodies $A$ and $B$ having equal surface area. On the surface of $A, n$ photons of frequency $f$ are incident perpendicularly in a time $t$. On the surface of $B$, $2 n$ photons of frequency $3 f$ are incident perpendicularly in a time $4 t$. The ratio of average intensity of radiation on surface $A$ to that on surface $B$ is

A photon released by the transition of an electron from the second excited state to the ground state of Hydrogen atom is incident on the surface of a metal of work function 3.1 eV . The de-Broglie wavelength of the most energetic electron emitted from that metal surface is nearly

The de-Broglie wavelength of a particle moving with a speed of $0.8 c$ is equal to the wavelength of a photon. If $c$ is speed of the photon in vacuum, the ratio of the energy of the photon and the kinetic energy of the particle is

The graph given in the figure shows the variation of photo current $(I)$ and the applied voltage ( $V$ ) for two different materials and for two different intensities of the incident radiations. Then the curves which represent the same material are

Radiations of wavelength 400 nm incidents on a photosensitive material of work function 2.2 eV . The stopping potential is nearly

Let $v_1$ and $v_2$ be the maximum velocities of the emitted electrons when the surface of a metal is illuminated with light waves of energy $E_1=4 \mathrm{eV}$ and $E_2=2.5 \mathrm{eV}$,respectively. If the work function of the metal is 2 eV , then the ratio $\frac{v_1}{v_2}$ is

Photons of energy 2.4 eV and wavelength $\lambda$ fall on a metal plate and release photoelectrons with a maximum velocity $v$. By decreasing $\lambda$ by $50 \%$, the maximum velocity of photoelectrons becomes $3 v$. The work function of the material of the metal plate is

The de-Broglie wavelength of an electron with kinetic energy of 320 eV is (take, $h=6.0 \times 10^{-34}$ SI unit, mass of electron $=m_c=9.0 \times 10^{-31} \mathrm{~kg}$, charge of an electron $=1.6 \times 10^{-19} \mathrm{C}$ )

In a photoelectric experiment, the wavelength of the light incident on the metal is changed from 200 nm to 400 nm . The decrease in the stopping potential is close to

[use $h c=1240 \mathrm{eV}$-nm, where $h=$ Planck's constant and $c$ is velocity of light]

The de-Broglie wavelength associated with an electron, accelerated through a potential difference of 121 V is about

(take, Plank's constant $=h=6.6 \times 10^{-34} \mathrm{Js}$, mass of electron $=9 \times 10^{-31} \mathrm{~kg}$ )

Light strikes a metal surface causing photoelectric emission. The wavelength of incident light is 248 nm . If the stopping potential for the ejected electrons is 2.8 eV , then the work function of the metal is (take, $h c=1240 \mathrm{eV}-\mathrm{nm}$ )

When monochromatic light falls on a photo sensitive metal, an electron is emitted with maximum velocity $1.6 \times 10^6 \mathrm{~m} / \mathrm{s}$. Find the stopping potential.

[charge of electron $=1.6 \times 10^{-19} \mathrm{C}$, mass of electron $\left.=9 \times 10^{-31} \mathrm{~kg}\right]$

A lamp of power 942 W radiates energy uniformly in all direction. The wavelength of radiation is 660 nm .The photon flux on a small screen 5.0 m from the lamp in units of photon $/ \mathrm{m}^2 \mathrm{~s} Q$ is

(take Planck's constant, $h=6.6 \times 10^{-34}$ SI unit)

Statement I By increasing the potential difference between cathode and anode continuously in a photoelectric experiment, the photocurrent always increases continuously.

Statement II If two photons $A$ and $B$ of energies 2.5 eV and 3.5 eV respectively, fall on a metal surface of work function 2.0 eV , then the ratio of maximum kinetic energies emitted between $A$ and $B$ is 3 .

Statement III The maximum energy needed by an electron to come out from a metal surface is called the work function of the metal.

Which of the following is correct?

Which of the following has the largest de-Broglie wavelength?