JEE Main 2022 (Online) 26th July Evening Shift | Atoms and Nuclei Question 141 | Physics

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

$$0.02 \min ^{-1}$$

$$2.7 \min ^{-1}$$

$$0.063 \min ^{-1}$$

$$6.3 \min ^{-1}$$

JEE Main 2022 (Online) 25th July Evening Shift

MCQ (Single Correct Answer)

-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)

$$\sqrt{\frac{\lambda \mathrm{R}}{\lambda-1}}$$

$$\sqrt{\frac{\lambda \mathrm{R}}{\lambda \mathrm{R}-1}}$$

$$\sqrt{\frac{\lambda}{\lambda \mathrm{R}-1}}$$

$$\sqrt{\frac{\lambda R^{2}}{\lambda R-1}}$$

JEE Main 2022 (Online) 25th July Morning Shift

MCQ (Single Correct Answer)

-1

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

(Symbols have their usual meanings)

$$\frac{\mathrm{nh}}{2 \pi \mathrm{r}}$$

$$ \frac{n h}{2 r} $$

$$ \frac{\mathrm{nh}}{2 \pi} $$