A closed organ pipe and an open organ pipe are tuned to the same fundamental frequency. The ratio of their lengths is

• 1 : 1

• 2 : 1

• 1 : 4

• 1 : 2

An observer standing near the sea shore os 54 /min. If the wavelength of the water wave is 10 m then the velocity of water wave is

• 540 ms^-1

• 5.4 ms^-1

• 0.184 ms^-1

• 9 ms^-1

A set of 24 tuning forks are so arranged that each gives 6 beats/s with the previous one. If the frequency of the last tuning fork is double that of the first, frequency of the second tuning fork is

• 138 Hz

• 132 Hz

• 144 Hz

• 276 Hz

A 10 Ω electric heater operates on a 110 V line. The rate at which heat is developed in watts is

• 1310 W

• 670 W

• 810 W

• 1210 W

For a certain thermocouple, if the temperature of the cold junction is 0°C, the neutral temperature and inversion temperatures are 285°C and 570°C respectively. If the cold junction is brought to 10°C, then the new neutral and inversion temperatures are respectively

• 285°C and 560°C

• 285°C and 570°C

• 295°C and 560°C

• 275°C and 560°C

The frequency of X-rays, γ-rays and ultraviolet rays are respectively a, b and c then

• a < b, b > c

• a > b, b > c

• a > b, b < c

• a < b, b < c

37.

If c is the speed of electromagnetic waves in vacuum, its speed in a medium of dielectric constant K and relative permeability μ_r is

• $\mathrm{v} = \frac{1}{\sqrt{{\mathrm{\mu }}_{\mathrm{r}}\mathrm{K}}}$

• $\mathrm{v} = \mathrm{c}\sqrt{{\mathrm{\mu }}_{\mathrm{r}}\mathrm{K}}$

• $\mathrm{v} = \frac{\mathrm{c}}{\sqrt{{\mathrm{\mu }}_{\mathrm{r}}\mathrm{K}}}$

• $\mathrm{v} = \frac{\mathrm{K}}{\sqrt{{\mathrm{\mu }}_{\mathrm{r}}\mathrm{c}}}$

The waves relevant to telecommunications are

• visibe light

• infrared

• ultraviolet

• microwave

The electrostatic field due to a charged conductor just outside the conductor is

• zero and parallel to the surface at every point inside the conductor

• zero and is normal to the surface at every point inside the conductor

• parallel to the surface at every point and zero inside the conductor

• normal to the surface at every point and zero inside the conductor

A point charge + q is placed at the midpoint of a cube of side a. The electric flux emerging from the cube is

• zero

• $\frac{3{\mathrm{qa}}^2}{{\mathrm{\epsilon }}_0}$

• $\frac{\mathrm{q}}{{\mathrm{\epsilon }}_0}$

• $\frac{{\mathrm{\epsilon }}_0}{4{\mathrm{qa}}^2}$