If the diameter of a carbon atom is 0.15 nm, the number of carbon atoms that can be placed side by side in a straight line across the length of the scale of length 20 cm long will be:

$$\begin{gathered} 1. 1.33 \times {10}^7 \\ 2. 5.46 \times {10}^8 \\ 3. 1.33 \times {10}^9 \\ 4. 2.36 \times {10}^8 \end{gathered}$$

The charge on the oil drop is –1.282 × 10^–18C. The number of electrons present in it would be 

1. 15

2. 8

3. 2

4. 6

An element with a mass number of 81 contains 31.7% more neutrons as compared to protons. The atomic symbol of the element would be

$$\begin{gathered} 1. {}_{35}{}^{81}\mathrm{Br} \\ 2. {}_{36}{}^{81}\mathrm{Br} \\ 3. {}_{35}{}^{79}\mathrm{Br} \\ 4. {}_{36}{}^{79}\mathrm{Br} \end{gathered}$$

An ion with a mass number of 56 contains 3 units of positive charge and 30.4% more neutrons than electrons. The symbol of the ion is -

$$\begin{gathered} 1. {}_{26}{}^{56}\mathrm{Fe}^{+3} \\ 2. {}_{26}{}^{57}\mathrm{Fe}^{+3} \\ 3. {}_{27}{}^{58}\mathrm{Fe}^{+3} \\ 4. {}_{25}{}^{56}\mathrm{Fe}^{+3} \end{gathered}$$

A nitrogen laser produces radiation at a wavelength of 337.1 nm. If the number of photons emitted is 5.6 × 10²⁴, the power of the laser is:

$$\begin{gathered} 1. 4.56 \times {10}^7 \mathrm{J} \\ 2. 3.33 \times {10}^6 \mathrm{J} \\ 3. 1.29 \times {10}^6 \mathrm{J} \\ 4. 9.17 \times {10}^5 \mathrm{J} \end{gathered}$$

If the photon detector receives a total of 3.15$\times {10}^{-18}$ J from the radiation of 600 nm, the number of photons received by the detector would be 

$$\begin{gathered} 1. {10}^2 \\ 2. 10 \\ 3. 50 \\ 4. 20 \end{gathered}$$

A radiation source emitted  2.5 × 10¹⁵ photons in 2 nanoseconds. Energy of the source is -

$$\begin{gathered} 1. 8.28 \times {10}^{-10} \mathrm{J} \\ 2. 8.24 \times {10}^{10} \mathrm{J} \\ 3. 7.12 \times {10}^{-11} \mathrm{J} \\ 4. 2.12 \times {10}^{ 10} \mathrm{J} \end{gathered}$$

Emission transitions in the Paschen series end at orbit n = 3 and start from orbit n and can be represented as v = 3.29 × 10¹⁵ (Hz)$\left(\frac{1}{3^2}- \frac{1}{{\mathrm{n}}^2}\right)$. The value of n if the transition is observed at 1285 nm is
1. 6
2. 5
3. 8
4. 9

If the velocity of the electron is 1.6 × 10⁶ ${\mathrm{ms}}^{-1}$. The de Broglie wavelength associated with this electron is 

$$\begin{gathered} 1. 590 \mathrm{pm} \\ 2. 455 \mathrm{pm} \\ 3. 512 \mathrm{pm} \\ 4. 401 \mathrm{pm} \end{gathered}$$

If the wavelength of a neutron is 800 pm, then the characteristic velocity associated with the neutron is

1. 494 m s^-1
2. 567 m s^-1
3. 494 cm s^-1
4. 501 m s^-1