The number of photons of light with a wavelength of 4000 pm that provide 1J of energy would be 

$$\begin{gathered} 1. 2.01 \times {10}^{16} \\ 2. 2.01 \times {10}^{19} \\ 3. 4.14 \times {10}^{23} \\ 4. 2.14 \times {10}^{21} \end{gathered}$$

Electromagnetic radiation of wavelength 242 nm is just sufficient to ionise sodium atom. The ionisation energy of sodium in kJ mol^-1 is -

1. 494

2. 4.94

3. 516

4. 0.50

A 25-watt bulb emits monochromatic yellow light with a wave length of 0.57µm. The rate of emission of quanta per second would be
$1. 7.17 \times {10}^{-19} {\mathrm{s}}^{-1}$
2. 4.13 × 10¹⁶ s^-1
3. 7.17 × 10¹⁹ s^-1
4. 1.26 × 10²⁰ s^-1

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 -

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

The wavelength of the light emitted when the electron returns to the ground state in the H atom, from n = 5 to n = 1, would be: (The ground-state electron energy is –2.18 × 10^-18 j)
1. Wavelength = 9.498 x 10^-8 km
2. Wavelength = 12.498 x 10^-8 m
3. Wavelength = 9.498 x 10^-8 m
4. Wavelength = 9.498 x 10^-8 cm

The neon gas emits radiation of 616 nm. The number of quanta that are present in 2 J of energy is

$$\begin{gathered} 1. 6.2 \times {10}^{-18} \\ 2. 5.6 \times {10}^{17} \\ 3. 6.2 \times {10}^{18} \\ 4. 32.2 \times {10}^{-20} \end{gathered}$$