31.

An α-particle and a proton moving with the same kinetic energy enter a region of uniform magnetic field at right angles to the field. The ratio of the radii of the paths of α-particle to that of the proton is

• 1 : 8

• 1 : 1

• 1 : 2

• 1 : 4

Direction of current induced in a wire moving in a magnetic field is found using

• Right hand clasp rule

• Fleming's left hand rule

• Fleming's right hand rule

• Ampere's rule

An ideal resistance R, ideal inductance L, ideal capacitance C and AC voltmeters ,V₁, V₃ and V₄ are connected to an AC sources as shown in figure. At resonance

• reading in V₂ = reading in V₃

• reading in V₃ =reading in V₁

• reading in V₁ = reading in V₂

• reading in V₂ = reading in V₄

X-rays, gamma rays and microwaves travelling in vacuum have

• same velocity and same frequency

• same wavelengths but different velocities

• same frequency but different velocities

• same velocity but different wavelengths

A point source of light is kept below the surface of water (n_w = 4 /3) at a depth $\sqrt{7}$ m. The radius of the circular bright patch of light noticed on the surface of water is

• $\sqrt{7} \mathrm{m}$

• $\frac{3}{\sqrt{7}} \mathrm{m}$

• 3 m

• $\frac{\sqrt{7}}{3} \mathrm{m}$

A monochromatic beam of light is travelling from medium A of refractive index n₁ to a medium B of refractive index n₂. In the medium A, there are x number of waves in certain distance. In the medium B, there are y number of waves in the same distance. Then, refractive index of medium A with respect to medium B is

• $\frac{\mathrm{x}}{\mathrm{y}}$

• $\frac{\mathrm{y}}{\mathrm{x}}$

• $\sqrt{\frac{\mathrm{x}}{\mathrm{y}}}$

• $\frac{\mathrm{x}}{\mathrm{y} - \mathrm{x}}$

In Young's double slit experiment, fringes of width β are produced on a screen kept at a distance of 1 m from the slit. When the screen is moved away by 5 x 10^-2 m, fringe width changes by 3 x 10^-5 m. The separation between the slits is 1 x 10^-3 m The wavelength of the light used is

• 400 nm

• 500 nm

• 600 nm

• 700 nm

For sustained interference fringes in double slit experiment, essential condition/s is/are

1. sources must be coherent.
2. the intensities of the two sources must be equal.

Here, the correct option/s is/are

• Neither (1) nor (2)

• Both (1) and (2)

• Only (1)

• Only (2)

In single slit experiment, the width of the slit is reduced. Then, the line width of the principal maxima

• decreases but becomes less bright

• increases but becomes less bright

• decreases but becomes more bright

• increases but becomes more bright

A proton and an alpha particle are accelerated under the same potential difference. The ratio of de-Broglie wavelengths of the proton and the alpha particle is

• 2

• $\sqrt{8}$

• $\frac{1}{\sqrt{8}}$

• 1