Q9 / 75 · JEE Main 2026 (23 January Shift 2) · Chemistry
Identify the INCORRECT statements from the following:
A. Notation ${ }_{12}^{24} \mathrm{Mg}$ represents 24 protons and 12 neutrons.
B. Wavelength of a radiation of frequency $4.5 \times 10^{15} \mathrm{~s}^{-1}$ is $6.7 \times 10^{-8} \mathrm{~m}$.
C. One radiation has wavelength $=\lambda_{1}(900 \mathrm{~nm})$ and energy $=\mathrm{E}_{1}$. Other radiation has wavelength $=\lambda_{2}(300 \mathrm{~nm})$ and energy $=\mathrm{E}_{2}. \mathrm{E}_{1}: \mathrm{E}_{2}=3: 1$.
D. Number of photons of light of wavelength 2000 pm that provides 1 J of energy is $1.006 \times 10^{16}$.
Choose the correct answer from the options given below:
A. Notation ${ }_{12}^{24} \mathrm{Mg}$ represents 24 protons and 12 neutrons.
B. Wavelength of a radiation of frequency $4.5 \times 10^{15} \mathrm{~s}^{-1}$ is $6.7 \times 10^{-8} \mathrm{~m}$.
C. One radiation has wavelength $=\lambda_{1}(900 \mathrm{~nm})$ and energy $=\mathrm{E}_{1}$. Other radiation has wavelength $=\lambda_{2}(300 \mathrm{~nm})$ and energy $=\mathrm{E}_{2}. \mathrm{E}_{1}: \mathrm{E}_{2}=3: 1$.
D. Number of photons of light of wavelength 2000 pm that provides 1 J of energy is $1.006 \times 10^{16}$.
Choose the correct answer from the options given below:
- AB and C Only
- BA and D Only
- Correct answerCA and C Only
- DA and B Only
Solution
Checking each statement:
(A) states $_{12}^{24}Mg$ has 24 protons, but the mass number is 24 and atomic number is 12, so this is INCORRECT.
(B) Using $\lambda = \frac{c}{f} = \frac{3 \times 10^8}{4.5 \times 10^{15}} = 6.67 \times 10^{-8}$ m, which is CORRECT.
(C) For $\lambda_1 = 900$ nm and $\lambda_2 = 300$ nm, since energy is inversely proportional to wavelength, $E_1:E_2 = 1:3$, not $3:1$ as stated, so this is INCORRECT.
(D) For photons at $\lambda = 2000$ pm, energy per photon is $E = \frac{hc}{\lambda} = 9.94 \times 10^{-17}$ J, giving $N = 1.006 \times 10^{16}$ photons for 1 J, which is CORRECT.
The incorrect statements are A and C.
(A) states $_{12}^{24}Mg$ has 24 protons, but the mass number is 24 and atomic number is 12, so this is INCORRECT.
(B) Using $\lambda = \frac{c}{f} = \frac{3 \times 10^8}{4.5 \times 10^{15}} = 6.67 \times 10^{-8}$ m, which is CORRECT.
(C) For $\lambda_1 = 900$ nm and $\lambda_2 = 300$ nm, since energy is inversely proportional to wavelength, $E_1:E_2 = 1:3$, not $3:1$ as stated, so this is INCORRECT.
(D) For photons at $\lambda = 2000$ pm, energy per photon is $E = \frac{hc}{\lambda} = 9.94 \times 10^{-17}$ J, giving $N = 1.006 \times 10^{16}$ photons for 1 J, which is CORRECT.
The incorrect statements are A and C.
Hence, the correct answer is option: 'C'.