Verified Solution • 2025–26 Session moderate

QJEEM24Ph89bb: JEE Main 2024 Physics - Class 12 JEEM24Ph89bb Solution: A particular hydrogen-like ion emits the radiation of frequency …

A particular hydrogen-like ion emits the radiation of frequency 3×1015 Hz3 \times 10^{15} \mathrm{~Hz} when it makes transition from n=2n=2 to n=1n=1 . The frequency of radiation emitted in transition from n=3n=3 to n=1n=1 is x9×1015 Hz\frac{x}{9} \times 10^{15} \mathrm{~Hz} , when x=x= ________ .

Step-by-Step Verified Solution

The emission frequency of radiation from a hydrogen-like ion during electron transitions can be understood using the formula derived from Rydberg's equation for hydrogen-like atoms, which is given as:

E=E0h(1n12−1n22)E = \frac{E_0}{h} \left( \frac{1}{n^2_1} - \frac{1}{n^2_2} \right)

where:

  • EE is the energy of the emitted photon,
  • E0E_0 is the Rydberg constant for hydrogen,
  • hh is Planck's constant,
  • n1n_1 and n2n_2 are the principal quantum numbers for the initial and final energy levels, respectively, with n_2 < n_1 .

Given a transition from n=2n=2 to n=1n=1 emits radiation with a frequency of 3×1015 Hz3 \times 10^{15} \mathrm{~Hz} , we can write:

ν1=3×1015 Hz\nu_1 = 3 \times 10^{15} \mathrm{~Hz}

For the transition from n=3n=3 to n=1n=1 , we can use the same principle to find the frequency of the emitted radiation, ν2\nu_2 , which will depend on the difference in energy levels involved in the transition. The frequency is directly proportional to this energy difference, so we can compare the two transitions using their respective frequencies:

ν2ν1=(1n1f2−1n1i2)(1n2f2−1n2i2)=(112−132)(112−122)=(1−19)(1−14)\frac{\nu_2}{\nu_1} = \frac{\left( \frac{1}{n_{1f}^2} - \frac{1}{n_{1i}^2} \right)}{\left( \frac{1}{n_{2f}^2} - \frac{1}{n_{2i}^2} \right)} = \frac{\left( \frac{1}{1^2} - \frac{1}{3^2} \right)}{\left( \frac{1}{1^2} - \frac{1}{2^2} \right)} = \frac{\left(1 - \frac{1}{9}\right)}{\left(1 - \frac{1}{4}\right)}

After simplification:

ν23×1015=(89)(34)=3227\frac{\nu_2}{3 \times 10^{15}} = \frac{\left(\frac{8}{9}\right)}{\left(\frac{3}{4}\right)} = \frac{32}{27}

Thus, to find the frequency u2u_2 for the transition from n=3n=3 to n=1n=1 :

ν2=329×1015Hz\nu_2 = \frac{32}{9} \times 10^{15} \mathrm{Hz}

Hence, in the given formula x9×1015 Hz\frac{x}{9} \times 10^{15} \mathrm{~Hz} for the frequency, xx is equal to 3232 .

Related Learning Resources & Exam Preparation