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. \(1.47\times10^{-34}~\text{m}\)$\mathrm{}$

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. \(9.371 ~\times 10^{-31}\)
2. \(9.001 ~\times 10^{-31}\)
3. \(1.675 ~\times 10^{-31}\)
4. \(2.705 ~\times 10^{-31}\)

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 \(550~\text{nm}\) (average wavelength) for yellow-green colour. Three materials with work functions are given as \(Al~(4.28~\text{eV}),\) \(Cu~(4.65~\text{eV})\) and \(Na~(2.75~\text{eV}).\) 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