A 200 W sodium street lamp emits yellow light of wavelength 0.6 $\mathrm{\mu m}$. If it is 25% efficient in converting electrical energy to light, how many photons of yellow light does it emit per second?

1. $1.5\times {10}^{20}$

2. $6\times {10}^{18}$

3. $62\times {10}^{20}$

4. $3\times {10}^{19}$

In the photoelectric emission process from a metal of work function 1.8 eV, the kinetic energy of most energetic electrons is 0.5 eV. What is the corresponding stopping potential?

1. 1.3 V

2. 0.5 V

3. 2.3 V

4. 1.8 V

A source S₁ is producing, 10¹⁵ photons per sec of wavelength 5000 Å. Another source S₂ is producing 1.02×10¹⁵ photons per second of wavelength 5100 Å. Then the ratio of the power of S₂ to the power of S₁ is equal to:

Monochromatic light of frequency 6.0×10¹⁴ Hz is produced by a laser. The power emitted is 2×10^-3 W. What will be the average number of photons emitted by the source per second?

1. $5\times {10}^{15}$

2. $5\times {10}^{16}$

3. $5\times {10}^{17}$

4. $5\times {10}^{14}$

When photons of energy h$\nu$ fall on an aluminium plate (of work function E₀), photoelectrons of maximum kinetic energy K are ejected. If the frequency of the radiation is doubled, the maximum kinetic energy of the ejected photoelectrons will be:

1. $K+E_0$

2. 2K

3. K

4. K+h$\nu$

In an experiment of the photoelectric effect, the wavelength of incident radiation is $\lambda$. The wavelength of incident radiation is reduced to $\frac{1}{3}$rd of initial value and the maximum kinetic energy of photoelectron is observed to be n times the previous value. What will be the threshold wavelength for the metal plate?
1. \(\frac{n-1}{n-3} \lambda \)
2. \(\frac{n}{n-3} \lambda \)
3. \(\frac{n-3}{n-1} \lambda \)
4. \(\frac{n+1}{n-3} \lambda\)

The de-Broglie wavelength of a particle accelerated by a 150 volt potential difference is 10^-10 m. What will its wavelength be if it is accelerated by a 600 volt potential difference?

1. 0.25 $\stackrel{o}{A}$

2. 0.5 $\stackrel{o}{A}$

3. 1.5 $\stackrel{o}{A}$

4. 2 $\stackrel{o}{A}$

Light of a frequency of \(1.5\) times the threshold frequency is incident on a photosensitive material. What happens to the photoelectric current when the frequency is cut in half and the intensity is doubled?

An electron is accelerated from rest through a potential difference of \(V\) volt. If the de Broglie wavelength of an electron is $\mathrm{}$\(1.227\times10^{-2}~\text{nm}\). what will be its potential difference?
1. \(10^{2}~\text{V}\)
2. \(10^{3}~\text{V}\)
3. \(10^{4}~\text{V}\)
4. \(10^{5}~\text{V}\)