11.

The maximum particle velocity in a wave motion is half the wave velocity. Then the amplitude of the wave is equal to

• $\frac{\mathrm{\lambda }}{4\mathrm{\pi }}$

• $\frac{2\mathrm{\lambda }}{\mathrm{\pi }}$

• $\frac{\mathrm{\lambda }}{2\mathrm{\pi }}$

• λ

The ratio of the velocity of sound in hydrogen $\left(\mathrm{\gamma } = \frac{7}{5}\right)$ to that in helium $\left(\mathrm{\gamma } = \frac{5}{3}\right)$ at the same temperature is

• $\sqrt{\frac{5}{42}}$

• $\sqrt{\frac{5}{21}}$

• $\frac{\sqrt{42}}{5}$

• $\frac{\sqrt{21}}{5}$

An engine moving towards a wall with a velocity 50 ms^-1 emits a note of 1.2 kHz. Speed of sound in air is 350 ms^-1. The frequency of the note after reflection from the wall as heard by the driver of the engine is

• 2.4 kHz

• 0.24 kHz

• 1.6 kHz

• 1.2 kHz

A glass tube is open at both the ends. A tuning fork of frequency f resonates with the air column inside the tube. Now the tube is placed vertically inside water so that half the length of the tube is filled with water. Now the air column inside the tube is in unison with another fork of frequency f'. Then

• f' = f

• f' = 4f

• f' = 2f

• $\mathrm{f}\text{'} = \frac{\mathrm{f}}{2}$

The surface temperature of the sun which has maximum energy emission at 500 nm is 6000 K. The temperature of a star which has maximum energy emission at 400 nm will be

• 8500 K

• 4500 K

• 7500 K

• 6500 K

All components of the electromagnetic spectrum in vacuum have the same

• energy

• velocity

• wavelength

• frequency

In the Wheatstone's network given, P = 10 Ω, Q = 20 Ω, R = 15 Ω, S =30 Ω, the current passing through the battery (of negligible internal resistance) is

• 0.36 A

• zero

• 0.18 A

• 0.72 A

A circular coil carrying a certain current produces a magnetic field B₀ at its centre. The coil is now rewound so as to have 3 turns and the same current is passed through it. The new magnetic field at the centre is

• $\frac{{\mathrm{B}}_0}{9}$

• 9B₀

• $\frac{{\mathrm{B}}_0}{3}$

• 3B₀

A proton and a deuteron with the same initial kinetic energy enter a magnetic field in a direction perpendicular to the direction of the field. The ratio of the radii of the circular trajectories described by them is

• 1 : 4

• $1 : \sqrt{2}$

• 1 : 1

• 1 : 2

Two tangent galvanometers A and B have coils of radii 8 cm and 16 cm respectively and resistance 8 Ω each. They are connected in parallel wth a cell of emf 4 V and negligible internal resistance. The deflections produced in the tangent galvanometers A and B are 30° and 60° respectively. If A has 2 turns, then B must have

• 18 turns

• 12 turns

• 6 turns

• 2 turns