21.

The graph between wave number  $\left(\overrightarrow{\mathrm{\nu }}\right)$  and angular frequency  ( ω ) is

•  

•  

•  

• 

The breaking stress of a wire depends upon

• length of  the wire

• material of the wire

• radius of the wire

• shape of the cross-section

The density of a substance  at  0^°C  is 10 g/cc and at  100^° C, its density is  9.7  g/cc. The coefficient of linear expansion of the substance is

• 10^-4

• 10²

• 10^-3

• 10²

Scent sprayer is based on

• Charle's law

• Archimedes principle

• Boyle's law

• Bernoulli's theorem

According to Wein's displacement law

• λT = constant

• λ/T  = constant

• λ ∝  ( 1/ T² )

• both (b) and (c)

A black body is at a temperature 300 K. It emits energy at a rate, which is proportional to

• 300

• (300)³

• (300)²

• (300)⁴

The latent heat of vapourisation of water is  2240. If the work done in the process of vapourisation of 1 g is 168 J, then increase in internal energy is

• 2408 J

• 2072 J

• 2240 J

• 1904 J

The velocities of sound at the same temperature in two monoatomic gases of densities ρ₁ and  ρ₂ and  ν₁ and  ν₂ respectively. If  ρ₁ / ρ₂ = 4, then the value of  ν₁/ ν₂  is

• 1/4

• 2

• 1/2

• 4

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

Assertion:  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.