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JEE Advance | PYQ

In a radioactive decay chain reaction, \( {}^{230}_{90}\mathrm{Th} \) nucleus decay into \( {}^{214}_{84}\mathrm{Po} \) nucleus. The ratio of the number of \( \alpha \) to number of \( \beta^{-} \) particles emitted in this process is _____.

Two resistance \( R_1 = X\Omega \) and \( R_2 = 1\Omega \) are connected to a wire AB of uniform resistivity, as shown in the figure. The radius of the wire varies linearly along its axis from \( 0.2 \, \text{mm} \) at A to \( 1 \, \text{mm} \) at B. A galvanometer (G) connected to the centre of the wire, \( 50 \, \text{cm} \) from each end along its axis, shows zero deflection when A and B are connected to a battery. The value of \( X \) is _____.

In a particular system of units, a physical quantity can be expressed in terms of the electric charge \( e \), electron mass \( m_e \), Planck’s constant \( h \), and Coulomb’s constant \( k = \dfrac{1}{4\pi \varepsilon_0} \), where \( \varepsilon_0 \) is the permittivity of vacuum. In terms of these physical constants, the dimension of the magnetic field is \( [B] = [e]^{\alpha}[m_e]^{\beta}[h]^{\gamma}[k]^{\delta} \). The value of \( \alpha + \beta + \gamma + \delta \) is ____.

Consider a configuration of \( n \) identical units, each consisting of three layers. The first layer is a column of air of height \( h = \dfrac{1}{3} \, \text{cm} \), and the second and third layers are of equal thickness \( d = \dfrac{\sqrt{3}-1}{2} \, \text{cm} \), and refractive indices \( \mu_1 = \sqrt{\dfrac{3}{2}} \) and \( \mu_2 = \sqrt{3} \), respectively. A light source O is placed on the top of the first unit, as shown in the figure. A ray of light from O is incident on the second layer of the first unit at an angle of \( \theta = 60^{\circ} \) to the normal. For a specific value of \( n \), the ray of light emerges from the bottom of the configuration at a distance \( l = \dfrac{8}{\sqrt{3}} \, \text{cm} \), as shown in the figure. The value of \( n \) is ____.

A charge \( q \) is surrounded by a closed surface consisting of an inverted cone of height \( h \) and base radius \( R \), and a hemisphere of radius \( R \) as shown in the figure. The electric flux through the conical surface is \( \dfrac{nq}{6\,\in_{0}} \) (in SI units). The value of \( n \) is _______.

On a frictionless horizontal plane, a bob of mass \( m = 0.1\,\text{kg} \) is attached to a spring with natural length \( l_0 = 0.1\,\text{m} \). The spring constant is \( k_1 = 0.009\,\text{N}\,\text{m}^{-1} \) when the length of the spring \( l > l_0 \) and is \( k_2 = 0.016\,\text{N}\,\text{m}^{-1} \) when \( l < l_0 \). Initially the bob is released from \( l = 0.15\,\text{m} \). Assume that Hooke’s law remains valid throughout the motion. If the time period of the full oscillation is \( T = (n\pi)\,\text{s} \), then the integer closest to \( n \) is ____.

An object and a concave mirror of focal length \( f = 10\,\text{cm} \) both move along the principal axis of the mirror with constant speeds. The object moves with speed \( V_0 = 15\,\text{cm}\,\text{s}^{-1} \) towards the mirror with respect to a laboratory frame. The distance between the object and the mirror at a given moment is denoted by \( u \). When \( u = 30\,\text{cm} \), the speed of the mirror \( V_m \) is such that the image is instantaneously at rest with respect to the laboratory frame, and the object forms a real image. The magnitude of \( V_m \) is ____ \( \text{cm}\,\text{s}^{-1} \).

In the figure, the inner (shaded) region A represents a sphere of radius \( r_A = 1 \), within which the electrostatic charge density varies with the radial distance \( r \) from the centre as \( \rho_A = k r \), where \( k \) is positive. In the spherical shell B of outer radius \( r_B \), the electrostatic charge density varies as \( \rho_B = \dfrac{2k}{r} \). Assume that dimensions are taken care of. All physical quantities are in their SI units.

Which of the following statement(s) is (are) correct?

In Circuit-1 and Circuit-2 shown in the figures, \( R_1 = 1\Omega \), \( R_2 = 2\Omega \) and \( R_3 = 3\Omega \). \( P_1 \) and \( P_2 \) are the power dissipations in Circuit-1 and Circuit-2 when the switches \( S_1 \) and \( S_2 \) are in open conditions, respectively. \( Q_1 \) and \( Q_2 \) are the power dissipations in Circuit-1 and Circuit-2 when the switches \( S_1 \) and \( S_2 \) are in closed conditions, respectively.


Which of the following Statement(s) is (are) correct?

A bubble has surface tension \( S \). The ideal gas inside the bubble has ratio of specific heats \( \gamma = \dfrac{5}{3} \). The bubble is exposed to the atmosphere and it always retains its spherical shape. When the atmospheric pressure is \( P_{a1} \), the radius of the bubble is found to be \( r_1 \) and the temperature of the enclosed gas is \( T_1 \). When the atmospheric pressure is \( P_{a2} \), the radius of the bubble and the temperature of the enclosed gas are \( r_2 \) and \( T_2 \), respectively.
Which of the following statement(s) is(are) correct?

A disk of radius \( R \) with uniform positive charge density \( \sigma \) is placed on the \( xy \) plane with its center at the origin. The Coulomb potential along the \( z \)-axis is \( V(z)=\dfrac{\sigma}{2\epsilon_{0}}\left(\sqrt{R^{2}+z^{2}}-z\right) \). A particle of positive charge \( q \) is placed initially at rest at a point on the \( z \) axis with \( z=z_{0} \) and \( z_{0}>0 \). In addition to the Coulomb force, the particle experiences a vertical force \( \vec{F}=-c\hat{k} \) with \( c>0 \). Let \( \beta=\dfrac{2c\,\in_{0}}{q\sigma} \). Which of the following statement(s) is(are) correct?

A double slit setup is shown in the figure. One of the slits is in medium \( 2 \) of refractive index \( n_{2} \). The other slit is at the interface of this medium with another medium \( 1 \) of refractive index \( n_{1}( \neq n_{2}) \). The line joining the slits is perpendicular to the interface and the distance between the slits is \( d \). The slit widths are much smaller than \( d \). A monochromatic parallel beam of light is incident on the slits from medium \( 1 \). A detector is placed in medium \( 2 \) at a large distance from the slits, and at an angle \( \theta \) from the line joining them, so that \( \theta \) equals the angle of refraction of the beam. Consider two approximately parallel rays from the slits received by the detector.

Which of the following statement(s) is(are) correct?

In the given P–V diagram, a monoatomic gas \(\left( \gamma = \dfrac{5}{3}\right) \) is first compressed adiabatically from state \( A \) to state \( B \). Then it expands isothermally from state \( B \) to state \( C \). [Given: \( \left(\dfrac{1}{3}\right)^{0.6} \simeq 0.5 \), \( \ln 2 \simeq 0.7 \)]

Which of the following statement(s) is(are) correct?

A flat surface of a thin uniform disk \( A \) of radius \( R \) is glued to a horizontal table. Another thin uniform disk \( B \) of mass \( M \) and with the same radius \( R \) rolls without slipping on the circumference of \( A \), as shown in the figure. A flat surface of \( B \) also lies on the plane of the table. The center of mass of \( B \) has fixed angular speed \( \omega \) about the vertical axis passing through the center of \( A \). The angular momentum of \( B \) is \( n M \omega R^2 \) with respect to the center of \( A \). Which of the following is the value of \( n \)?

When light of a given wavelength is incident on a metallic surface, the minimum potential needed to stop the emitted photoelectrons is \( 6.0 \, \text{V} \). This potential drops to \( 0.6 \, \text{V} \) if another source with wavelength four times that of the first one and intensity half of the first one is used. What are the wavelength of the first source and the work function of the metal, respectively? [Take \( \dfrac{hc}{e} = 1.24 \times 10^{-6} \, \text{J m C}^{-1} \)].

Area of the cross-section of a wire is measured using a screw gauge. The pitch of the main scale is \( 0.5 \, \text{mm} \). The circular scale has \( 100 \) divisions and for one full rotation of the circular scale, the main scale shifts by two divisions. The measured readings are listed below.

What are the diameter and cross-sectional area of the wire measured using the screw gauge?

Which one of the following options represents the magnetic field \( \vec{B} \) at \( O \) due to the current flowing in the given wire segments lying on the \( xy \) plane?