The maximum kinetic energy of photoelectron emitted from the surface of work function f due to incidence of light of frequency n is E. If the frequency of incident light is doubled, then maximum kinetic of emitted photon will be

1.  2E

2.  2E - f

3.  2E + f

4.  2E + 2f

The de-Broglie associated with an electron accelerated through a voltage of 900 V is 

1.  $0.31 \stackrel{\mathrm{o}}{\mathrm{A}}$

2.  $0.41 \stackrel{\mathrm{o}}{\mathrm{A}}$

3.  $0.5 \stackrel{\mathrm{o}}{\mathrm{A}}$

4.  $0.16 \stackrel{0}{\mathrm{A}}$

$$\begin{gathered} \mathrm{A} 200\mathrm{W} \mathrm{sodium} \mathrm{street} \mathrm{lamp} \mathrm{emits} \mathrm{yellow} \mathrm{light} \mathrm{of} \mathrm{wavelength} 0.60\mathrm{\mu m}. \mathrm{Assuming} \mathrm{it} \mathrm{to} \mathrm{be} \\ 50\% \mathrm{efficient}, \mathrm{in} \mathrm{converting} \mathrm{electrical} \mathrm{energy} \mathrm{into} \mathrm{light}, \mathrm{the} \mathrm{number} \mathrm{of} \mathrm{photons} \mathrm{of} \mathrm{yellow} \\ \mathrm{light} \mathrm{emitted} \mathrm{per} \mathrm{second} \mathrm{is} \mathrm{nearly} \mathrm{equal} \mathrm{to}- \end{gathered}$$

1.  $3 x {10}^{19}$

2.  $3 x {10}^{20}$

3.  $1.5 x {10}^{20}$

4.  $6 x {10}^{20}$

Monochromatic radiation emitted when an electron in a hydrogen atom jumps from the first excited state to the ground state irradiates a photosensitive material. The stopping potential is found to be 4V. The threshold wavelength of the material is-

1.  $2 \mathrm{x} {10}^{-7}\mathrm{m}$

2.  $2 \mathrm{x} {10}^{-6}\mathrm{m}$

3.  $4 \mathrm{x} {10}^{-7}\mathrm{m}$

4.  $4 \mathrm{x} {10}^{-6}\mathrm{m}$

In a photoelectric experiment using a metal of work function 1.8 eV, if the maximum kinetic energy of emitted electrons is 1.5eV, then the corresponding value to stopping potential is:

1.  1.8V

2.  3.3V

3.  0.3V

4.  1.5V

Electrons used in an electron microscope are accelerated by a voltage of 25 kV. If the accelerating voltage is reduced to 6.25 kV, the resolving power of the microscope would :

1. Increase to 4 time

2. Increases to 2 times

3. Decrease to half

4. Decrease to 1/4th

When the light of wavelength $\mathrm{\lambda }$ is used in a photoelectric experiment, the maximum kinetic energy of emitted electrons is found to be K. What will the maximum kinetic energy of the photoelectrons when the light of wavelength $\frac{\mathrm{\lambda }}{2}$ is used instead of $\mathrm{\lambda }$:

1. Zero

2. Non zero but less than 2 K

3. 2K

4. More than 2K

The concept of matter-wave was given by-

1.  de-Broglie

2.  Einstein

3.  Maxwell

4.  Bohr

When the light of wavelength $\mathrm{\lambda } = 3100 \stackrel{\mathrm{o}}{\mathrm{A}}$ is made to fall on metal in a photoelectric experiment, the maximum kinetic energy of emitted electrons is found to be 2.5eV. The work function of the metal is:

1.  2.5eV

2.  3.1eV

3.  0.9eV

4.  1.5eV

If the momentum of a photon is p, then its energy is :

1.  pc

2.  $\frac{1}{2}\mathrm{pc}$

3.  $\frac{{\mathrm{p}}^2}{2\mathrm{c}}$

4.  $\frac{1}{4}\mathrm{pc}$