A radioactive nucleus emits 4 $\alpha$ -particles and 7 $\beta$-particles in succession. The ratio of number of neutrons of that of protons is [A= mass number, Z= atomic number]

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1

A radioactive nucleus emits 4 $\alpha$ -particles and 7 $\beta$-particles in succession. The ratio of number of neutrons of that of protons is [A= mass number, Z= atomic number]

2

An obstacle is moving towards the source with velocity v. The sound is reflected from the obstacle. If c is the speed of sound and $\lambda$ is the wavelength, then the wavelength of the reflected wave, $\lambda_{r}$is

3

In a communication system, a repeater is used to extend the range to transmission. It is the combination of

4

The light of wavelength $\lambda$ incident on the surface of metal having work function $\phi$ emits the electrons. The maximum velocity of electrons emitted is

[c= velocity of light, h= planck's constant, m= mass of electron]

5

A spherical rubber balloon carries a charge, uniformly distributed over the surface. As the balloon is blown up and increase in size. The total electric flux coming out of the surface

6

A absolute zero temperature, pure silicon behaves as

7

Five capacitors each of capacity C are connected as shown in the figure. If their resultant capacity is 2 $\mu$ F, then the capacity of each condenser is

8

In conversion of moving coil galvanometer into an ammeter of required range, the resistance of ammeter , so formed is

[ S= shunt and G= resistance of galvanometer]

9

In the system of two particles of masses m_{1} and m_{2}, the first particle is moved by a distance d towards the centre of mass.To keep the centre of mass unchanged, the second particle will have to be moved by a distance

10

If the maximum kinetic energy of emitted electrons in photoelectric effect is 3.2 x 10^{-19} J and the work-function for metal is

6.63 x10^{-19 }J, then stopping potential and threshold wavelength respectively are

[Planck's constant,h=6.63 x10^{34} J-s]

[ Velocity of light , c=3 x10^{8} m/s]

[charge on electron =1.6 x10^{-19} C]

11

Two cells having unknown emf E_{1 }and E_{2} (E_{1} > E_{2}) are connected in a potentiometer circuit,to assist each other. The null point obtained is at 490 cm from the higher potential end. When cell E_{2} is connected, so as to oppose cell E_{1}, the null point is obtained at 90 cm from the same end, the ratio of the EMFs of two cells $\left(\frac{E_{1}}{E_{2}}\right)$ is

12

Two bodies A and B of equal mass are suspended from two separate massless springs of force constant k_{1} and k_{2}, respectively. The bodies oscillate vertically such that their maximum velocities are equal. The ratio of the amplitudes of body A to that of body B is

13

A uniform wire has length L mass M and density $\rho$ . it is under tension T and v is the speed of transverse wave along the wire. The area of cross-section of the wire is

14

The Brewster's angle for the glass-air interface is (54.74) °. If a ray of light passing from air to glass strikes at an angle of incidence 45°, then the angle of refraction is

$[\tan (54.74)^{0}=\sqrt{2},\sin 45=\frac{1}{\sqrt{2}}]$

15

A body of mass 64 g is made to oscillate turn by turn on two different springs A and B. spring A and B has a force constant 4$\frac{N}{m}$ and 16 $\frac{N}{m}$ respectively. If T_{1} and T_{2} are period of oscillations of spring A and B respectively , Then $\frac{T_{1}+T_{2}}{T_{1}-T_{2}}$ will be

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