1
JEE Main 2022 (Online) 26th July Morning Shift
MCQ (Single Correct Answer)
+4
-1
Out of Syllabus

The disintegration rate of a certain radioactive sample at any instant is 4250 disintegrations per minute. 10 minutes later, the rate becomes 2250 disintegrations per minute. The approximate decay constant is :

$$\left(\right.$$Take $$\left.\log _{10} 1.88=0.274\right)$$

A
$$0.02 \min ^{-1}$$
B
$$2.7 \min ^{-1}$$
C
$$0.063 \min ^{-1}$$
D
$$6.3 \min ^{-1}$$
2
JEE Main 2022 (Online) 25th July Evening Shift
MCQ (Single Correct Answer)
+4
-1

Hydrogen atom from excited state comes to the ground state by emitting a photon of wavelength $$\lambda$$. The value of principal quantum number '$$n$$' of the excited state will be : ($$\mathrm{R}:$$ Rydberg constant)

A
$$\sqrt{\frac{\lambda \mathrm{R}}{\lambda-1}}$$
B
$$\sqrt{\frac{\lambda \mathrm{R}}{\lambda \mathrm{R}-1}}$$
C
$$\sqrt{\frac{\lambda}{\lambda \mathrm{R}-1}}$$
D
$$\sqrt{\frac{\lambda R^{2}}{\lambda R-1}}$$
3
JEE Main 2022 (Online) 25th July Morning Shift
MCQ (Single Correct Answer)
+4
-1

The momentum of an electron revolving in $$\mathrm{n}^{\text {th }}$$ orbit is given by :

(Symbols have their usual meanings)

A
$$\frac{\mathrm{nh}}{2 \pi \mathrm{r}}$$
B
$$\frac{n h}{2 r}$$
C
$$\frac{\mathrm{nh}}{2 \pi}$$
D
$$\frac{2 \pi r}{\mathrm{nh}}$$
4
JEE Main 2022 (Online) 25th July Morning Shift
MCQ (Single Correct Answer)
+4
-1

The magnetic moment of an electron (e) revolving in an orbit around nucleus with an orbital angular momentum is given by :

A
$$\vec{\mu}_{\mathrm{L}}=\frac{\overrightarrow{\mathrm{eL}}}{2 \mathrm{~m}}$$
B
$$\vec{\mu}_{\mathrm{L}}=-\frac{\overrightarrow{\mathrm{eL}}}{2 \mathrm{~m}}$$
C
$$\vec{\mu}_{l}=-\frac{\overrightarrow{e L}}{\mathrm{~m}}$$
D
$$\vec{\mu}_{l}=\frac{2 \overrightarrow{\mathrm{eL}}}{\mathrm{m}}$$
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