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

A parallel beam of light of wavelength $$900 \mathrm{~nm}$$ and intensity $$100 \,\mathrm{Wm}^{-2}$$ is incident on a surface perpendicular to the beam. The number of photons crossing $$1 \mathrm{~cm}^{2}$$ area perpendicular to the beam in one second is :

A
$$3 \times 10^{16}$$
B
$$4.5 \times 10^{16}$$
C
$$4.5 \times 10^{17}$$
D
$$4.5 \times 10^{20}$$
3
JEE Main 2022 (Online) 26th July Morning Shift
MCQ (Single Correct Answer)
+4
-1
Change Language

In Young's double slit experiment, the fringe width is $$12 \mathrm{~mm}$$. If the entire arrangement is placed in water of refractive index $$\frac{4}{3}$$, then the fringe width becomes (in mm):

A
16
B
9
C
48
D
12
4
JEE Main 2022 (Online) 26th July Morning Shift
MCQ (Single Correct Answer)
+4
-1
Change Language

The magnetic field of a plane electromagnetic wave is given by :

$$ \overrightarrow{\mathrm{B}}=2 \times 10^{-8} \sin \left(0.5 \times 10^{3} x+1.5 \times 10^{11} \mathrm{t}\right) \,\hat{j} \mathrm{~T}$$.

The amplitude of the electric field would be :

A
$$6\, \mathrm{Vm}^{-1}$$ along $$x$$-axis
B
$$3\, \mathrm{Vm}^{-1}$$ along $$z$$-axis
C
$$6\, \mathrm{Vm}^{-1}$$ along $$z$$-axis
D
$$2 \times 10^{-8} \,\mathrm{Vm}^{-1}$$ along $$z$$-axis
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