A rectangular film of liquid is extended from (4 cm $$ \times $$ 2 cm) to (5 cm $$ \times $$ 4 cm). If the work done is 3 $$ \times $$ 10^$$-$$4 J, the value of the surface tension of the liquid is

Three liquids of densities $$\rho $$₁, $$\rho $$₂  and $$\rho $$₃ (with $$\rho $$₁ > $$\rho $$₂ > $$\rho $$₃), having the same value of surface tension T, rise to the same height in three identical capillaries. The angles of contact $$\theta $$₁, $$\theta $$₂ and $$\theta $$₃ obey

Coefficient of linear expansion of brass and steel rods are $$\alpha $$₁ and $$\alpha $$₂. Lengths of brass and steel rods are $$l$$₁ and $$l$$₂ respectively. If ($$l$$₁ $$-$$ $$l$$₂) is maintained same at all temperatures, which one of the following relations holds good?

A black body is at a temperature of 5760 K. The energy of radiation emitted by the body at wavelength 250 nm is U₁, at wavelength 500 nm is U₂ and that at 1000 nm is U₃. Wien's constant, b = 2.88 $$ \times $$ 10⁶ nm K. Which of the following is correct ?