1986 年

When observed through a microscope, smoke particles in a smoke cell are seen to be in continuous random motion. This is mainly due to

Which of the following graphs correctly shows the relation between the pressure ($P$) and the volume ($V$) of a fixed mass of gas under constant temperature ?

The graph shows the cooling curve of liquid naphthalene. In which region has naphthalene completely solidified ?

If the pressure of a fixed mass of gas of initial volume $V$ is doubled and its absolute temperature halved, its volume becomes

Straight waves in a ripple tank are observed using a hand stroboscope with a single slit. The maximum frequency of rotation of the stroboscope where a stationary pattern can be observed is $2$ revolutions per second. The distance between the first crest and the eleventh crest is found to be $0.2$ m. What is the speed of the wave ?

The depth of a lake can be found by the method of echo-sounding. The depth of a short pulse sent vertically down to the bottom of the lake was received after $0.6$ s. Given that the speed of sound in water is $1440\ \mathrm{m\,s^{-1}}$, the depth of the lake will be

The diagram shows two conducting spheres $X$ and $Y$ mounted on insulating stands. Sphere $X$ carries positive charges and sphere $Y$ carries negative charges. As $Y$ is moved slowly towards $X$ (but without touching $X$) the total charges on $X$