1
JEE Main 2022 (Online) 29th June Morning Shift
+4
-1

The activity of a radioactive material is 2.56 $$\times$$ 10$$-$$3 Ci. If the half life of the material is 5 days, after how many days the activity will become 2 $$\times$$ 10$$-$$5 Ci ?

A
30 days
B
35 days
C
40 days
D
25 days
2
JEE Main 2022 (Online) 28th June Evening Shift
+4
-1

Let K1 and K2 be the maximum kinetic energies of photo-electrons emitted when two monochromatic beams of wavelength $$\lambda$$1 and $$\lambda$$2, respectively are incident on a metallic surface. If $$\lambda$$1 = 3$$\lambda$$2 then :

A
$${K_1} > {{{K_2}} \over 3}$$
B
$${K_1} < {{{K_2}} \over 3}$$
C
$${K_1} = {{{K_2}} \over 3}$$
D
$${K_2} = {{{K_1}} \over 3}$$
3
JEE Main 2022 (Online) 28th June Evening Shift
+4
-1

Following statements related to radioactivity are given below :

(A) Radioactivity is a random and spontaneous process and is dependent on physical and chemical conditions.

(B) The number of un-decayed nuclei in the radioactive sample decays exponentially with time.

(C) Slope of the graph of loge (no. of undecayed nuclei) Vs. time represents the reciprocal of mean life time ($$\tau$$).

(D) Product of decay constant ($$\lambda$$) and half-life time (T1/2) is not constant.

Choose the most appropriate answer from the options given below :

A
(A) and (B) only
B
(B) and (D) only
C
(B) and (C) only
D
(C) and (D) only
4
JEE Main 2022 (Online) 28th June Morning Shift
+4
-1

The de Broglie wavelengths for an electron and a photon are $$\lambda$$e and $$\lambda$$p respectively. For the same kinetic energy of electron and photon, which of the following presents the correct relation between the de Broglie wavelengths of two ?

A
$${\lambda _p} \propto \lambda _e^2$$
B
$${\lambda _p} \propto {\lambda _e}$$
C
$${\lambda _p} \propto \sqrt {{\lambda _e}}$$
D
$${\lambda _p} \propto \sqrt {{1 \over {{\lambda _e}}}}$$
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Mechanics
Electricity
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Modern Physics
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