111.

Standing waves are formed on a string when interference occurs between two waves  having

• the same amplitude travelling in the same direction with no phase difference between them

• the same amplitude, travelling in the opposite direction with no phase difference between them

• different amplitudes travelling in the same direction

• different amplitudes travelling in the opposite direction

The length of two open organ pipes are l and (l+ Δl) respectively. Neglecting end corrections the beats frequency between them will be approximately

• $\frac{\mathrm{v}}{2\mathrm{l}}$

• $\frac{\mathrm{v}}{4\mathrm{l}}$

• $\frac{\mathrm{v}∆\mathrm{l}}{2{\mathrm{l}}^2}$

• $\frac{\mathrm{v}∆\mathrm{l}}{\mathrm{l}}$

For the stationary wave

      $\mathrm{y} = \mathrm{u} \sin \left(\frac{\mathrm{\pi x}}{15}\right) \cos 96\mathrm{\pi t}$

The distance between a node and the next antinode is

• 7.5 cm

• 15 cm

• 22.5 cm

• 30 cm

A tuning fork produce 2 beats when sounded with one oscillator of frequency 514 Hz, and produces 6 beats with the other oscillator of frequency 510 Hz. The frequency of tuning fork is

• 516 Hz

• 510 Hz

• 514 Hz

• 520 Hz

To hear the echo in 1 s, the minimum distance of the source from the reflecting surface should be

• 28 m

• 18 m

• 19 m

• 165 m

Sound waves produced in gas are

• longitudinal

• transversal

• stationary

• progressive

Intensity of a source of a 100 cd at a distance 2 m is

• 25 lux

• 50 lux

• 75 lux

• 150 lux

Equation of a progressive sound wave is y = a sin $\left(400 \mathrm{\pi t} - \frac{\mathrm{\pi x}}{0.85}\right)$ where x in (metre), t (second), then frequency of wave is

• 200 Hz

• 400 Hz

• 500 Hz

• 600 Hz

Wavelength of the wave in the above question is

• 1.7 m

• 8.5 m

• 0.85 m

• 0.17 m

Relation of wavelengths of sound and light is

• λ_S < λ_L

• λ_S > λ_L

• λ_S = λ_L

• None of these