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

1.		2.
3.		4.

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

Light with an energy flux of \(25\times 10^{4}~\text{Wm}^{-2}\) falls on a perfectly reflecting surface at normal incidence. If the surface area is \(15~\text{cm}^2\), then the average force exerted on the surface is:
1. \(1.25\times 10^{-6}~\text{N}\)
2. \(2.5\times 10^{-6}~\text{N}\)
3. \(1.2\times 10^{-6}~\text{N}\)
4. \(3.0\times 10^{-6}~\text{N}\)

What will be the percentage change in the de-Broglie wavelength of the particle if the kinetic energy of the particle is increased to \(16\) times its previous value?
1. \(25\)
2. \(75\)
3. \(60\)
4. \(50\)

A 200W sodium street lamp emits yellow light of wavelength $0.6<mspace\; width="1em"></mspace>\mu m.$ 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. $3\times {10}^{19}$

Monochromatic radiation emitted when electron on hydrogen atom jumps from first excited to the ground state irradiates a photosensitive material. The stopping potential is measured to be 3.57 V. The threshold frequency of the material is:

1. $4\times {10}^{15}Hz$                               

2. $5\times {10}^{15}Hz$

3.$\mathrm{ 1}.6\times {10}^{15}Hz$                           

4. $2.5\times {10}^{15}Hz$