Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason(R).
Assertion (A) : Magnetic monopoles do not exist.
Reason (R) : Magnetic field lines are continuous and form closed loops.
In the light of the above statements, choose the most appropriate answer from the options given below :

An electron with mass ' \(m\) ' with an initial velocity \((\mathrm{t}=0) \overrightarrow{\mathrm{v}}=\mathrm{v}_0 \hat{\mathrm{i}} \quad\left(\mathrm{v}_0 \gt 0\right)\) enters a magnetic field \(\vec{B}=B_0 \hat{j}\). If the initial de-Broglie wavelength at \(\mathrm{t}=0\) is \(\lambda_0\) then its value after time ' t ' would be :

Wires \({W}_{1}\) and \({W}_{2}\) are made of same material having the breaking stress of \(1.25 \times 10^{9} \,{N} / {m}^{2}\) \({W}_{1}\) and \({W}_{2}\) have cross-sectional area of \(8 \times 10^{-7}\, {m}^{2}\) and \(4 \times 10^{-7}\, {m}^{2}\), respectively. Masses of \(20 \,{kg}\) and \(10\, {kg}\) hang from them as shown in the figure. The maximum mass that can be placed in the pan without breaking the wires is \(.....{kg}\) (Use \(\left.{g}=10\, {m} / {s}^{2}\right)\)

Two beams of light having intensities \(I\) and \(4\,I\) interfere to produce a fringe pattern on a screen. The phase difference between the two beams are \(\pi / 2\) and \(\pi / 3\) at points \(A\) and \(B\) respectively. The difference between the resultant intensities at the two points is \(x I\). The value of \(x\) will be.

A fish rising vertically upward with a uniform velocity of \(8\,ms ^{-1}\), observes that a bird is diving vertically downward towards the fish with the velocity of \(12\,ms ^{-1}\). If the refractive index of water is \(\frac{4}{3}\), then the actual velocity of the diving bird to pick the fish, will be \(.......\,ms ^{-1}\).

An object is allowed to fall from a height \(R\) above the earth, where \(R\) is the radius of earth. Its velocity when it strikes the earth's surface, ignoring air resistance, will be :

Two blocks of masses \(m\) and \(M,(M \gt m)\), are placed on a frictionless table as shown in figure. A massless spring with spring constant k is attached with the lower block. If the system is slightly displaced and released then
(\(\mu=\) coefficient of friction between the two blocks)

(A) The time period of small oscillation of the two blocks is \(\mathrm{T}=2 \pi \sqrt{\frac{(\mathrm{~m}+\mathrm{M})}{\mathrm{k}}}\)
(B) The acceleration of the blocks is \(\mathrm{a}=\frac{\mathrm{kx}}{\mathrm{M}+\mathrm{m}}\) (\(\mathrm{x}=\) displacement of the blocks from the mean position)
(C) The magnitude of the frictional force on the upper block is \(\frac{m \mu|x|}{M+m}\)
(D) The maximum amplitude of the upper block, if it does not slip, is \(\frac{\mu(M+m) g}{k}\)
(E) Maximum frictional force can be \(\mu(\mathrm{M}+\mathrm{m}) \mathrm{g}\).
Choose the correct answer from the options given below:

The distance of the point \((7,10,11)\) from the line \(\frac{x-4}{1}=\frac{y-4}{0}=\frac{z-2}{3}\) along the line \(\frac{x-9}{2}=\frac{y-13}{3}=\frac{z-17}{6}\) is

A plane is inclined at an angle \(\alpha  = 30^o\) with respect to the horizontal. A particle is projected with a speed \(u = 2\,ms^{-1},\) from the base of the plant, making an angle \(\theta = 15^o\) with respect to the plane as shown in the figure. The distance from the base at which the particle hits the plane is close to  ........ \(cm\) (Take \(g = 10\,ms^2\) )

Let \(f\) be a continuous function satisfying \(\int \limits_0^{t^2}\left( f ( x )+ x ^2\right) dx =\frac{4}{3} t ^3, \forall t > 0 . \quad\) Then \(f \left(\frac{\pi^2}{4}\right)\) equal to :

In a box, there are \(20\) cards, out of which \(10\) are lebelled as \(\mathrm{A}\) and the remaining \(10\) are labelled as \(B\). Cards are drawn at random, one after the other and with replacement, till a second \(A-\)card is obtained. The probability that the second \(A-\)card appears before the third \(B-\)card is

A diatomic gas, having \(C_{p}=\frac{7}{2} R\) and \(C _{ v }=\frac{5}{2} R ,\) is heated at constant pressure. The ratio \(dU : dQ : dW :\)

A simple pendulum has a bob with mass m and charge q. The pendulum string has negligible mass. When a uniform and horizontal electric field \( \vec{E} \) is applied, the final tension in the string changes.The final tension in the string, when pendulum attains an equilibrium position is __________ .
(g: acceleration due to gravity)