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What is the de-Broglie wavelength of a neutron in thermal equilibrium with heavy water at a temperature T (Kelvin) and mass m?
1. $\frac{h}{\sqrt{mkT}}$
2. $\frac{h}{\sqrt{3mkT}}$
3. $\frac{2h}{\sqrt{3mkT}}$ $$
4. $\frac{2h}{\sqrt{mkT}}$

When a metallic surface is illuminated with radiation of wavelength $\lambda$, the stopping potential is V. If the same surface is illuminated with radiation of wavelength 2$\lambda$, the stopping potential is $\frac{V}{4}$ .The threshold wavelength for metallic surface is:
(a) 5$\lambda$                (b)$\frac{5}{2}$$\lambda$
(c) 3$\lambda$                (d) 4$\lambda$

A radiation of energy 'E' falls normally on a perfectly reflecting surface. The momentum transferred to the surface is (c=velocity of light)
1. E/c
2. 2E/c
3. 2E/c²
4. E/c²

Light with a wavelength of 500 nm is incident on a metal with a work function of 2.28 eV. The de Broglie wavelength of the emitted electron will be:
1. \( <2.8 \times 10^{-10} \mathrm{~m} \)
2. \( <2.8 \times 10^{-9} \mathrm{~m} \)
3. \( \geq 2.8 \times 10^{-9} \mathrm{~m} \)
4. \( <2.8 \times 10^{-12} \mathrm{~m}\)

A 200W sodium street lamp emits yellow light of wavelength $0.6 \mu m.$ Assuming it to be 25% efficient in converting electrical energy to light, the number of photons of yellow light it emits per second is 
(1) $1.5\times {10}^{20}$                               
(2) $6\times {10}^{18}$
(3) $62\times {10}^{20}$                                 
(4) $3\times {10}^{19}$

In the Davisson and Germer experiment, the velocity of electrons emitted from the electron gun can be increased by
1. increasing the filament current
2. decreasing the filament current
3. decreasing the potential difference between the anode and filament
4. increasing the potential difference  between the anode and filament

Light of two different frequencies whose
photons have energies 1 eV and 2.5 eV
respectively illuminate a metallic surface 
whose function is 0.5 eV successively.
Ratio of maximum speeds of emitted 
electrons will be
(1) 1:2
(2) 1:1
(3) 1:5
(4) 1:4

When monochromatic radiation of intensity I falls on a metal surface, the number of photoelectrons and their maximum kinetic energy are N and T respectively. If the intensity of radiation is 2I what is the number of emitted electrons and their maximum kinetic energy?

The figure shows a plot of photo current versus anode potential for a photo sensitive surface for three difference radiations. Which one of the following is a correct statement?

(1) Curves a and b represent incident radiations of different frequencies and different intensities
(2) Curves a and b represent incident radiations of same frequency but of different intensities 
(3) Curves b and c represent incident radiations of different frequencies and different intensities
(4) Curves b and c represent incident radiations of same frequency having same intensity 

The work function of a surface of a photosensitive material is 6.2 eV. The wavelength of the incident radiation for which the stopping potential is 5V lies in the 
(1) ultraviolet region                               
(2) visible region
(3) infrared region                                   
(4) X-ray region 

An electron $\left(mass m\right)$ with an initial velocity v=${\mathrm{v}}_0\hat{\mathrm{i}} \left({\mathrm{v}}_0>0\right)$ is in an electric field E$=-E_0 \hat{i}\left(E_0=cons\tan t > 0\right).$ It's de Broglie wavelength at the time $t$ is given by:
(1) $\frac{{\lambda }_0}{\left(1+{\displaystyle \frac{e{E}_0}{m}}{\displaystyle \frac{t}{v_0}}\right)}$
(2) ${\lambda }_0\left(1+\frac{e{E}_{0}t}{m{v}_0}\right)$
(3) ${\lambda }_0$
(4)${\lambda }_{0}t.$

Work function of a metal is 2.1 eV. Which of the waves of the following wavelengths will be able to emit photoelectrons from its surface ?
(1) 4000 Å, 7500 Å                     
(2) 5500 Å, 6000 Å
(3) 4000 Å, 6000 Å                     
(4) None of these

The cathode of a photoelectric cell is changed such that the work function changes from ${\mathrm{W}}_1$ to ${\mathrm{W}}_2$ $\left({\mathrm{W}}_2>{\mathrm{W}}_1\right)$. If the current before and after the change are ${\mathrm{I}}_1$ and ${\mathrm{I}}_2$, all other conditions remaining unchanged, then (assuming $\mathrm{h\nu }>{\mathrm{W}}_2$) :
(1) ${\mathrm{I}}_1$= ${\mathrm{I}}_2$               
(2) ${\mathrm{I}}_1$< ${\mathrm{I}}_2$
(3) ${\mathrm{I}}_1$>${\mathrm{I}}_2$               
(4) ${\mathrm{I}}_1<{\mathrm{I}}_2<2{\mathrm{I}}_1$

The stopping potential \((V_{0})\) versus frequency \((\nu_{0})\) plot of a substance is shown in the figure. What will be the threshold wavelength?    
 

A plane electromagnetic wave of wave intensity 6 W/$m^2$ strikes a small mirror of area 30 $c{m}^2$, held perpendicular to the approaching wave. The momentum transferred in kg $m{s}^{-1}$ by the wave to the mirror each second will be
(1) $1.2\times {10}^{-10}$
(2) $2.4\times {10}^{-9}$
(3) $3.6\times {10}^{-8}$
(4) $4.8\times {10}^{-7}$