de Broglie wavelength λ associated with neutrons is related with absolute temperature T as

• λ ∝ T

• λ ∝ $\frac{1}{\mathrm{T}}$

• λ ∝ $\frac{1}{\sqrt{\mathrm{T}}}$

• λ ∝  T²

152.

Light with an energy flux of 18 W/cm² falls on a non-reflecting surface at normal incidence. The pressure exerted on the surface is

• 2 N/m²

• 2 × 10^-4 N/m²

• 6 N/m²

• 6 × 10^-4 N/m²

The dimensional formula of Planck's constant is

• [ M L² T^-1 ]

• [ M L² T^-2 ]

• [ M L⁰ T² ]

• [ M L T² ]

If  the  kinetic  energy  of  a  particle  is  increased  by  16  times,  the  percentage  change  in  the  de Broglie  wavelength  of  the particle  is

• 25 %

• 75 %

• 60 %

• 50 %

Assertion:  A photon has no rest mass, yet it carries definite momentum.

Reason:  Momemtum of photon is due to its energy and hence its equivalent mass.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false

Which of the following is matched wrongly?

• Oil drop experiment  → Millikan

• Dual nature of light → de Broglie

• Uncertainty principle → Heisenberg

• None of these

Assertion: Stopping potential depends upon the frequency of incident light but is independent of the intensity of the light. 

Reason:  The maximum kinetic energy of the photoelectrons is proportional to stopping potential.

• If both assertion and reason are true and reason is the correct explanation of assertion

• If both assertion and reason are true but reason is not the correct explanation of assertion

• If assertion is true but reason is false

• If both assertion and reason are false.

Hard X - rays for the study of fractures in bones should have a minimum wavelength of 10^-11 m. The accelerating voltage for electrons in X-ray machine should be

• < 124.2 kV

• > 124.2 kV

• between 60 kV and 70 kV

• = 100 kV

In photoelectric effect, the electrons are ejected from metals if the incident light has a certain minimum

• wavelength

• frequency

• amplitude

• angle of incidence

Flash light equipped with a new set of batteries, produces bright white light. As the batteries wear out

• the light intensity gets reduced with no change in its colour

• light colour changes first to yellow and then red with no change in intensity

• it stops working suddenly while giving white light

• colour changes to red and also intensity gets reduced