JEE Main 2026 — Chemistry Physical Chemistry

2026mcqmedium

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:

Official previous-year question

Held on 23 Jan 2026 · Verified 6 Jul 2026.

Options

A
B and C Only
B
A and D Only
C
A and C Only
D
A and B Only

Did you get this right?

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.

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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.

JEE Main 2026 — Chemistry Physical Chemistry

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Solution

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JEE Main 2026 — Chemistry Physical Chemistry

Options

Did you get this right?

Solution

Your note

JEE Main Physical Chemistry in other years

More JEE Main Physical Chemistry questions

Other Chemistry topics for JEE Main

Organic Chemistry

Inorganic Chemistry

Keep practicing Physical Chemistry