JEE Main 2025 (Online) 29th January Morning Shift | JEE Main Year Wise Previous Years Questions

JEE Main 2025 (Online) 29th January Morning Shift

MCQ (Single Correct Answer)

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Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A) : Emission of electrons in photoelectric effect can be suppressed by applying a sufficiently negative electron potential to the photoemissive substance.

Reason (R) : A negative electric potential, which stops the emission of electrons from the surface of a photoemissive substance, varies linearly with frequency of incident radiation.

In the light of the above statements, choose the most appropriate answer from the options given below :

Both (A) and (R) are true and (R) is the correct explanation of (A).

Both (A) and (R) are true but (R) is not the correct explanation of (A).

(A) is false but (R) is true

(A) is true but (R) is false

JEE Main 2025 (Online) 29th January Morning Shift

MCQ (Single Correct Answer)

-1

At the interface between two materials having refractive indices $n_1$ and $n_2$, the critical angle for reflection of an em wave is $\theta_{1C}$. The $\mathrm{n}_2$ material is replaced by another material having refractive index $n_3$ such that the critical angle at the interface between $n_1$ and $n_3$ materials is $\theta_{2 C}$. If $n_3>n_2>n_1 ; \frac{n_2}{n_3}=\frac{2}{5}$ and $\sin \theta_{2 C}-\sin \theta_{1 C}=\frac{1}{2}$, then $\theta_{1 C}$ is :

$ \sin^{-1}\left( \frac{1}{6n_1} \right) $

$ \sin^{-1}\left( \frac{1}{3n_1} \right) $

$ \sin^{-1}\left( \frac{5}{6n_1} \right) $

$ \sin^{-1}\left( \frac{2}{3n_1} \right) $

JEE Main 2025 (Online) 29th January Morning Shift

MCQ (Single Correct Answer)

-1

Match List - I with List - II.

List - I	List - II
(A) Electric field inside (distance r > 0 from center) of a uniformly charged spherical shell with surface charge density σ, and radius R.	(I) σ/ε₀
(B) Electric field at distance r>0 from a uniformly charged infinite plane sheet with surface charge density σ.	(II) σ/2ε₀
(C) Electric field outside (distance r>0 from center) of a uniformly charged spherical shell with surface charge density σ, and radius R.	(III) 0
(D) Electric field between 2 oppositely charged infinite plane parallel sheets with uniform surface charge density σ.	(IV) $\frac{\sigma}{\epsilon_0 r^2}$

Choose the correct answer from the options given below :

(A)-(IV), (B)-(I), (C)-(III), (D)-(II)

(A)-(II), (B)-(I), (C)-(IV), (D)-(III)

(A)-(III), (B)-(II), (C)-(IV), (D)-(I)

(A)-(IV), (B)-(II), (C)-(III), (D)-(I)

JEE Main 2025 (Online) 29th January Morning Shift

MCQ (Single Correct Answer)

-1

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A) : Choke coil is simply a coil having a large inductance but a small resistance. Choke coils are used with fluorescent mercury-tube fittings. If household electric power is directly connected to a mercury tube, the tube will be damaged.

Reason (R): By using the choke coil, the voltage across the tube is reduced by a factor $\left(R / \sqrt{R^2+\omega^2 L^2}\right)$, where $\omega$ is frequency of the supply across resistor $R$ and inductor $L$. If the choke coil were not used, the voltage across the resistor would be the same as the applied voltage.

In the light of the above statements, choose the most appropriate answer from the options given below :

(A) is true but (R) is false

Both $(\mathbf{A})$ and $(\mathbf{R})$ are true and $(\mathbf{R})$ is the correct explanation of $(\mathbf{A})$ 3.

Both $(\mathbf{A})$ and $(\mathbf{R})$ are true but $(\mathbf{R})$ is not the correct explanation of $(\mathbf{A})$

(A) is false but (R) is true