Physics MCQs for NEET — Practice Questions with Answers

The paragraph about Wien's law states: 'Light from the moon is found to have a maximum intensity near the wavelength $14 \mu m$. By Wien’s law, the surface of the moon is estimated to have a temperature of 200 K.'

The text explains: 'Internal energy is thus, the sum of molecular kinetic and potential energies in the frame of reference relative to which the centre of mass of the system is at rest. Thus, it includes only the (disordered) energy associated with the random motion of molecules of the system.' It further adds: 'The important thing about internal energy is that it depends only on the state of the system, not on how that state was achieved. Internal energy U of a system is an example of a thermodynamic ‘state variable’'.

According to the provided text, 'The gathering and focussing mechanism of light by the eye-lens is well described in the wave picture. But its absorption by the rods and cones (of the retina) requires the photon picture of light.' This directly indicates that the absorption by rods and cones involves the particle nature of light, i.e., photons.

The text states, 'He reasoned that nature was symmetrical and that the two basic physical entities – matter and energy, must have symmetrical character. If radiation shows dual aspects, so should matter.' This is the core reasoning behind de Broglie's hypothesis.

The de Broglie relation is given as $\lambda = h/p$, where h is Planck's constant and p is the momentum of the particle. (Equation 11.5 in the text: $\lambda = h/p = h/mv$).

The text mentions, 'Millikan’s first precise measurements confirmed the Einstein’s photoelectric equation and obtained an accurate value of Planck’s constant h. This led to the acceptance of particle or photon description (nature) of electromagnetic radiation, introduced by Einstein.'

The text states, 'The de Broglie wavelength ($\lambda$) is independent of the charge and nature of the material particle.'

The text indicates, 'It is significantly measurable (of the order of the atomic-planes spacing in crystals) only in case of sub-atomic particles like electrons, protons, etc. (due to smallness of their masses and hence, momenta).'

The section '2.5 t oWarDs QUantUm mecHanical moDel of tHe atom' states: 'Two important developments which contributed significantly in the formulation of such a model were: 1. Dual behaviour of matter, 2. Heisenberg uncertainty principle.'

The text under '13.4.1 Mass – Energy' clearly states, 'Einstein showed from his theory of special relativity that it is necessary to treat mass as another form of energy... Einstein gave the famous mass-energy equivalence relation $E = mc^2$ (13.6).'