Monochromatic light of frequency $6.0\times {10}^{14} \mathrm{Hz}$ is produced by a laser. The power emitted is $2.0\times {10}^{-3} \mathrm{W}.$ 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 \(5.4\times10^6~\text{m/s}\)?
1. \(0.244~\text{nm}\)
2. \(0.135~\text{nm}\)
3. \(0.157~\text{nm}\)
4. \(0.111~\text{nm}\)

The de Broglie wavelength associated with a ball of mass 150 g travelling at a speed of 30.0 m/s is:

$1. 1.47\times {10}^{-32} \mathrm{m}$
$2. 2.01\times {10}^{-34} \mathrm{m}$
$3. 2.01\times {10}^{-32} \mathrm{m}$
$4. 1.47\times {10}^{-34} \mathrm{m}$

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

1. Electron

2. $\alpha$-particle

3. proton

4. All have the same 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 \(100\) V?
1. \(0.123\) nm
2. \(0.232\) nm
3. \(0.031\) nm
4. \(0.312\) 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