When a metallic surface is illuminated with radiation of wavelength $\mathrm{\lambda }$, the stopping potential is V. If the same surface is illuminated with radiation of wavelength 2$\mathrm{\lambda }$, the stopping potential is $\frac{V}{4}$ . The threshold wavelength for the metallic surface is

1. 5$\mathrm{\lambda }$

2. $\frac{5}{2}\lambda$

3. 3$\mathrm{\lambda }$

4. 4$\mathrm{\lambda }$

 

A photoelectric surface is illuminated successively by the monochromatic light of wavelength $\mathrm{\lambda }$ and $\frac{\mathrm{\lambda }}{2}$. If the maximum kinetic energy of the emitted photoelectrons in the second case is 3 times that in the first case, the work function of the surface of the mineral is :
[h=Plank’s constant, c=speed of light]

1. $\frac{hc}{2\lambda }$

2. $\frac{hc}{\lambda }$

3. $\frac{2hc}{\lambda }$

4. $\frac{hc}{3\lambda }$

Light of wavelength 500 nm is incident on metal with work function 2.28 eV. The de-Broglie wavelength of the emitted electron is :

1. $<2.8\times {10}^{-10}m$

2. $<2.8\times {10}^{-9}m$

3. $\ge 2.8\times {10}^{-9}m$

4. $\le 2.8\times {10}^{-12}m$

Which of the following figures represent the variation of the particle momentum and the associated de-Broglie wavelength?

1. 

2. 

3. 

4. 

Light with an energy flux of 25 × 10⁴ Wm^–2 falls on a perfectly reflecting surface at normal incidence. If the surface area is 15 cm², the average force exerted on the surface is :

1. $1.25\times {10}^{-6}N$

2. $2.50\times {10}^{-6}N$

3. $1.20\times {10}^{-6}N$

4. $3.0\times {10}^{-6}N$

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

1. 0.65 eV

2. 1.0 eV

3. 1.3 eV

4. 1.5 eV

If the kinetic energy of the particle is increased to 16 times its previous value, the percentage change in the de-Broglie wavelength of the particle is :

1. 25

2. 75

3. 60

4. 50