Monochromatic light of frequency $6.0\times 10^{14}~\text{Hz}$ is produced by a laser. The power emitted is $2.0\times 10^{-3}~\text{W}$$\mathrm{}.$ How many photons per second, on average, are emitted by the source?
1. $6\times 10^{15}$
2. $5\times 10^{14}$
3. $6\times 10^{14}$
4. $5\times 10^{15}$

The work function of caesium is $2.14~\text{eV}$. The wavelength of incident light if the photocurrent is brought to zero by a stopping potential of $0.60~\text{V}$ will be:
1. $454~\text{nm}$
2. $440~\text{nm}$
3. $333~\text{nm}$
4. $350~\text{nm}$

The wavelength of light in the visible region is about 390 nm for violet colour. The energy of photons in (eV) is:
(Take $h=6.63\times 10^{-34}~\mathrm{Js}$ and $1\mathrm{eV}=1.6\times 10^{-19}~\mathrm{J}$)

1. 1.64 eV
2. 2.26 eV
3. 3.19 eV
4. 4.03 eV

What is the de-Broglie wavelength associated with an electron moving at a speed of $5.4\times10^6~\text{m/s}$?

The de-Broglie wavelength associated with a ball of mass $150~\text{g}$ travelling at a speed of $30.0~\text{m/s}$ is:
1. $1.47\times10^{-32}~\text{m}$
2. $2.01\times10^{-34}~\text{m}$
3. $2.01\times10^{-32}~\text{m}$
4. $1.47\times10^{-34}~\text{m}$

An electron, an $α\text-$particle, and a proton have the same kinetic energy. Which of these particles has the shortest de-Broglie wavelength?

A particle is moving three times as fast as an electron. The ratio of the de Broglie wavelength of the particle to that of the electron is $1.813\times {10}^{-4}$. The particle’s mass is:

$1. 9.371\times {10}^{-31} \mathrm{kg}$
$2. 9.001\times {10}^{-31} \mathrm{kg}$
$3. 1.675\times {10}^{-27} \mathrm{kg}$
$4. 2.705\times {10}^{-27} \mathrm{kg}$

What is the de Broglie wavelength associated with an electron, accelerated through a potential difference of $100~\text V?$ 
1. $0.123~\text{nm}$
2. $0.232~\text{nm}$
3. $0.031~\text{nm}$
4. $0.312~\text{nm}$

The wavelength of light in the visible region is about $550$ nm (average wavelength) for yellow-green colour. Three materials with work functions are given as Al ($4.28$ eV), Cu ($4.65$ eV) and Na ($2.75$ eV). From which of these photosensitive materials, can you build a photoelectric device that operates with visible light?
1. Al
2. Cu
3. Na
4. none of the above