CBSE
Multiple Choice QuestionsAssertion: Thin films such a soap bubble or a thin layer of oil on water show beautiful colours when illuminated by white light.
Reason: It happens due to the interference of light reflected from upper surface of the thin film.
If both the assertion and reason are true and reason is a correct explanation of assertion.
If both assertion and reason are true but assertion is not a correct explanation of the assertion.
If both the assertion is true but the reason is false.
If both assertion and reason are false.
The work done in increasing the size of a soap film from 10 cm x 6 cm to 10 cm x 11 cm is 3 x 10-4 J. The surface tension of the film is
1.5 × 10-2 N/m
3 × 10-2 N/m
6.0 × 10-2 N/m
11 × 10-2 N/m
The maximum force in addition to the weight required to pull a wire 5.0 cm long from the surface of the water at temperature 20°C, is 728 dyne. The surface tension of water is
7.28 N/cm
7.28 dyne/cm
72.8 dyne/cm
7.28 × 102 dyne/cm
A capillary tube of radius r is immersed in water and water rises in it to a height H. Mass of water in the capillary tube is m. If the capillary of radius 2r is taken and dipped in water, the mass of water that will rise in the capillary tube will be
m
2 m
m/2
4 m
The property utilized in the manufacture of lead shots is
specific weight of liquid lead
compressibility of liquid lead
specific gravity of liquid lead
surface tension of liquid lead
Which of the following physical wuantity do not have same dimensions?
pressure and stress
tension and surface tension
strain and angle
energy and work
Scent sprayer is based on
Charle's law
Archimedes principle
Boyle's law
Bernoulli's theorem
The length of a needle floating on water is 2.5 cm. Calculate the added force (due to surface tension) required to pull the needle out of water. (Surface tension of water = 7.2 10-2 N/m2)
3.6 10-3 N
3.4 10-10 N
3.0 10-5 N
3.8 10-11 N
Two small drops of mercury, each of radius R, coalesce to form a single large drop. The ratio of the total surface energies before and after change is
1 : 21/3
21/3 : 1
2 : 1
1 : 2
For liquid to rise in a capillary tube, the angle of contact should be
acute
obtuse
right
none of these
